<PAGE>

                                                                    EXHIBIT 4.15

                            SUBSCRIPTION OFFER LETTER

PRIVATE & CONFIDENTIAL

April 5, 2004

Squadram Limited
16/F., The Chinese Bank Building
61 Des Voeux Road Central
Hong Kong

Attention: Ms. Chen Hui

Dear Sirs,

DF CHINA TECHNOLOGY INC. (THE "COMPANY") -
PLACING OF 5,200,000 NEW SHARES (THE "SUBSCRIPTION SHARES")
IN THE ISSUED SHARE CAPITAL OF THE COMPANY AT US$0.4038 PER SHARE (THE
"SUBSCRIPTION PRICE") (THE "SUBSCRIPTION")

1.    INTRODUCTION

      We refer to our conversation, whereby we offered, subject to the terms and
      conditions set out below, to procure the sale to you 5,200,000 shares at
      the Subscription Price of US$0.4038 per Subscription Share (the
      "Subscription Shares") for the total subscription of US$2,100,000.00 and
      you orally accepted our offer and agreed irrevocably as principal to
      purchase the Subscription Shares.

      All capitalized terms used, but not otherwise defined herein shall have
      the meanings set for on Appendix A attached hereto.

2.    CONDITIONS

      Please note that the Subscription is conditional upon that immediately
      upon signing hereof, we shall proceed to notify the Listing Qualification
      Department of The NASDAQ Stock Market by the Notification Form for listing
      of Additional Shares.

3.    SETTLEMENT DATE

      Settlement is scheduled to take place on or before April 20, 2004 (the
      "Settlement Date").

4.    AMOUNT PAYABLE

                                       1
<PAGE>

      The total amount payable by you for your Subscription Shares is
      US$2,100,000.00 (or the equivalent amount in Renminbi currency).

5.    NOT A US PERSON; NOT AN AFFILIATE

      Upon your acceptance hereto, you shall confirm that you are not a US
      Person and confirm that in relation to your subscription of the
      Subscription Shares, you or your beneficial owner are not an Affiliate of
      the Company nor any directors, executive officers, or Beneficial Owners
      thereof or a member of the Shareholder Group thereof. In addition, you
      shall declare that your acceptance of our offer of the Subscription Shares
      is entirely of your own volition and that you are not acting upon the
      instruction of any such Affiliate. Also, your purchase of the Subscription
      Shares is not financed directly or indirectly by any such Affiliate.

6.    UNDERTAKINGS

      By your acceptance of our offer, you;

            (a) agree to make payment of US$2,100,000.00 in full for all the
            Subscription Shares by the Settlement Date, and that interest of 2%
            p.a. above the Hong Kong prime rate will be payable on any late
            settlement;

            (b) agree that you have not relied on any information,
            representation or warranty supplied or made by us or any one on
            behalf of ourselves or any other party involved in the Subscription
            and that you have made and will continue to make your own appraisal
            of the Subscription and the Subscription Shares and the other
            matters referred to in this letter;

            (c) agree and acknowledge that we do not make and have not made any
            warranty, representation or recommendation as to the merits of the
            Subscription Shares;

            (d) represent and warrant to us that you or beneficial owner are not
            US Person(s) or Affiliate(s) of the Company nor any directors,
            executive officers, or Beneficial Owners thereof or a member of a
            Shareholder Group thereof;

            (e) represent and warrant that you had at all material times and
            still have full power and authority to enter into the contract of
            the Subscription for your own account or for the account of one or
            more persons for whom you exercise investment discretion and your
            oral agreement to do so as recorded herein constitutes your valid
            and legally binding obligation and is enforceable in accordance with
            its terms.

      You will, whether before or after completion of the Subscription, continue
      to provide us information regarding the beneficial owner of the
      Subscription Shares acquired by you as required by applicable BVI law and
      US laws for delivery to the relevant regulatory authority or governmental
      agency.

                                       2
<PAGE>

      Information and personal data provided by you to us are connected with the
      Subscription and you shall observe any rules, legal or regulatory
      requirements including the disclosure of such data to certain regulatory
      bodies. Also, we may provide such data to any agent, representative and
      associate, which provide services in connection with the Subscription.

7.    GENERAL

      Any notification to be given by us to you shall be validly given if
      delivered by hand or sent by facsimile to the address and facsimile
      numbers set out in the attached Subscription Confirmation and shall be
      deemed to be given on delivery or (if given by facsimile) on due despatch.

      Your rights and obligations in respect of the Subscription will be
      incapable of rescission or termination by you. Time is of the essence of
      the Subscription.

      The Subscription recorded in this letter shall be governed by and
      construed in accordance with the laws of Hong Kong and we respectively
      submit to the non-exclusive jurisdiction of the courts of Hong Kong in
      respect thereof.

      NO AMENDMENT TO THE TERMS AND CONDITIONS OF THIS LETTER CAN BE ACCEPTED TO
      US.

8.    ACKNOWLEDGMENT

      Please complete and return the attached Subscription Confirmation with the
      duplicate of this letter to the undersigned at Hong Kong fax no. (852)
      2851 3660.

Yours faithfully,
For and on behalf of
DF CHINA TECHNOLOGY INC.

_______________________________________
Aaron Zhu Xiaojun
Executive Director and Chief Financial Officer

Encl.

                                       3
<PAGE>

                                                                      APPENDIX A

Capitalized terms used, but not otherwise defined in the Subscription Offer
Letter shall have the meanings set forth below:

"AFFILIATE"                means a person that directly, or indirectly through
                           one or more intermediaries, controls, or is
                           controlled by, or is under common control with, the
                           Company, a director an executive officer or a
                           Beneficial Owner.

"BENEFICIAL OWNER"         means any person who directly or indirectly is the
                           beneficial owner of more than five percent of a class
                           of the Company's securities.

"SHAREHOLDER GROUP"        means two or more persons act as a partnership,
                           limited partnership, syndicate, or other group for
                           the purpose of acquiring, holding, or disposing of
                           securities of the Company;

"US PERSON"                means:

                               a.   Any natural person resident in the United
                                    States;

                               b.   Any partnership or corporation organized or
                                    incorporated under the laws of the United
                                    States;

                               c.   Any estate of which any executor or
                                    administrator is a U.S. person;

                               d.   Any trust of which any trustee is a U.S.
                                    person;

                               e.   Any agency or branch of a foreign entity
                                    located in the United States;

                               f.   Any non-discretionary account or similar
                                    account (other than an estate or trust) held
                                    by a dealer or other fiduciary for the
                                    benefit or account of a U.S. person;

                               g.   Any discretionary account or similar account
                                    (other than an estate or trust) held by a
                                    dealer or other fiduciary organized,
                                    incorporated, or (if an individual) resident
                                    in the United States; and

                               h.   Any partnership or corporation if:

                                        (i)  Organized or incorporated under the
                                             laws of any foreign jurisdiction;
                                             and

                                        (ii) Formed by a U.S. person principally
                                             for the purpose of investing in
                                             securities not registered under the
                                             Act, unless it is organized or
                                             incorporated, and owned, by
                                             accredited investors (as defined in
                                             Rule 501(a)) who are not natural
                                             persons, estates or trusts.

                                       4
<PAGE>

                            SUBSCRIPTION CONFIRMATION

PRIVATE & CONFIDENTIAL

April 5, 2004

To    :     DF China Technology Inc.
            Units 3207-07, West Tower
            Shun Tak Centre
            Central, Hong Kong

Attn  :     Mr. Aaron Zhu Xiaojun
            Executive Director
            (Fax No: 2851 3660)

Dear Sirs,

DF CHINA TECHNOLOGY INC. (THE "COMPANY") -
PLACING OF 5,200,000 NEW SHARES (THE "PLACING SHARES")
IN THE ISSUED SHARE CAPITAL OF THE COMPANY AT US$0.4038 PER SHARE (THE
"PLACING PRICE") (THE "PLACING")

We refer to your Subscription Offer Letter dated April 5, 2004 (the
"Subscription Offer Letter") in relation to the captioned subject. Terms used in
this letter shall have the same meanings as defined in the Subscription Offer
Letter, unless the context requires otherwise.

We hereby confirm receipt of the Subscription Offer Letter, and acknowledge and
accept all the terms and conditions as set out therein and confirm that these
terms and conditions are those of our oral contract to your representative for
our/my subscription as principal from the Company of 5,200,000 subscription
shares (the "Subscription Shares") at the Subscription Price of US$0.4038 per
share for the total subscription of US$2,100,000.00 We undertake to pay the
consideration for the Subscription Shares of US$2,100,000.00 on or before the
Settlement Date as set out in the Subscription Offer Letter by a cashier order
drawn on a licensed bank in Hong Kong or China.

Further more, we hereby confirm that: -

(1)   We undertake to provide to you upon request such other information as may
      be required to be provided to the Securities and Exchange Commission (the
      "SEC") and NASDAQ;

(2)   We are not a US Person(s). We are a private investor whose main business
      involves the acquisition and disposal, or the holding, of shares and other
      securities as principal and the subscription of the Subscription Shares by
      us would not constitute a breach of the relevant laws;

                                       5
<PAGE>

(3)   We or our beneficial owner are not an Affiliate of the Company nor any
      directors, executive officers, or Beneficial Owners thereof or a member of
      a Shareholder Group thereof;

(4)   We are not financed or backed directly or indirectly by the Company, its
      directors, its Beneficial Owners or its executive officers or any of the
      Company's Affiliates;

(5)   We are not a person who is accustomed to taking instructions from any of
      the director, executive officers or Beneficial Owners of the Company or
      any of their Affiliates in relation to the acquisition, disposal, voting
      or any other disposition of securities in the Company;

(6)   We understand that information and personal data provided by us are
      required in relation to the Subscription and to observe any rules, legal
      or regulatory requirements including the disclosure of such data to
      certain regulatory bodies. Moreover, we shall provide such data to any
      governmental or regulatory bodies (including but not limited to the NASDAQ
      and the SEC);

(7)   We undertake to respond promptly, in writing, to questions raised by you
      relating to the Subscription.

(8)   No share of the Company was held by us prior to our entering into the
      agreement to participate as a subscriber in the Subscription;

(9)   In case of a default in payment, you shall reserve the right to charge
      interest on the net amount overdue calculated on the basis of 2% per
      month;

(10)  The details of the ULTIMATE BENEFICIAL OWNER(S) of the Subscription Shares
      subscribed through the Placing are as follows: -

      Name                :     Chen Hui

      Address             :     Flat 405, Block 33, Helen Garden,
                                Shekou Shenzhen,
                                Guangdong Province, China

      Passport #          :     W03680279

      Date of Birth       :     November 4, 1967

      Contact             :     86-13530590915

(11)  We set out below our details for registration of the Subscription
      Shares:-

      Name                               :     Squadram Limited
      Place of Incorporation             :     The British Virgin Islands
      Company Number/ID Number           :     IBC: 549244

                                       6
<PAGE>

      Registered/Residential Address     :     Beaufort House, P.O. Box 438,
                                               Road Town, Tortola, British
                                               Virgin Islands

      Correspondence Address             :     16/F., The Chinese Bank Building
                                               61 Des Voeux Road Central
                                               Hong Kong

We fully understand that our personal data set out above and any further
personal data relating to ourselves may be submitted to the SEC and NASDAQ and
hereby confirm that the data is true and accurate.

Yours faithfully,
For and behalf of
Squadram Limited

__________________________
Chen Hui
Director

Date: April 5, 2004

                                       7