<PAGE>   1
                                  AMENDMENT # 4

      To Lease dated October 9, 1992 between Welsh Edenvale Partners '86 (a
Minnesota limited partnership), as lessor and Stratasys, Inc. (a Delaware
corporation) as Lessee.

      THIS AGREEMENT TO LEASE, entered into and made as of July 27, 1998, by and
between Carpenter Land Company L.L.P., as Landlord and Stratasys, Inc., (a
Delaware corporation), as Lessee.

                                   WITNESSETH:

      WHEREAS, Lessor and Lessee have heretofore entered into a Lease Agreement
(hereinafter referred to as the "Lease"), dated October 9, 1992 for
office/warehouse space located at 14950 Martin Drive, Eden Prairie, Minnesota,
(hereinafter the "Demised Premises", commencing November 1, 1992; and

      WHEREAS, Carpenter Land Company, Landlord, purchased the building
including the Demised Premises on April 30, 1993; and

      WHEREAS, Landlord and Lessee amended the Lease on January 23, 1995 in
Amendment #1; and

      WHEREAS, Landlord and Lessee amended the Lease on June 22, 1995 in
Amendment #2; and

      WHEREAS, Landlord and Lessee amended the Lease on October 30, 1995 in
Amendment #3.

      NOW, THEREFORE, in consideration of rents reserved and of the covenants
and agreements herein set forth, it is agreed by Landlord and Lessee that the
Lease is hereby amended from and after the date hereof as follows:

1. TERM

      The lease term shall be extended by thirty-six (36) months, commencing on
      August 1, 1999 and terminating on July 31, 2002.

2. BASE RENT

      The base rent for the extension period shall be as follows:

<PAGE>   2

<TABLE>
<CAPTION>
                                    Base Rent
      Period                        Per Month               Annual Rent
      ------                        ---------               -----------
<S>                                 <C>                     <C>        
      August 1, 1999 through and
      including July 31, 2000       $13,938.00              $167,256.00

      August 1, 2000 through and
      including July 31, 2001       $14,519.00              $174,228.00

      August 1, 2001 through and
      including July 31, 2002       $15,100.00              $181,200.00
                                                            -----------

                                          TOTAL             $522,684.00
</TABLE>

3. IMPROVEMENTS

      The Landlord agrees to provide, at no expense to Lessee, the following
      improvements to the Demised Premises:

      o     Re-paint the building exterior in a mutually acceptable color.

      o     Provide a $5,000.00 allowance to be used to construct a new, lighted
            building monument sign.

      o     Overlay the asphalt in the loading area on the east side of the
            building.

      o     Modify the HVAC systems by adding two (2) new air conditioning
            units, new ducting and rebalance air flow to correct temperature and
            control deficiencies.

      The Landlord agrees to begin work on these improvements as soon as
      reasonably possible after this Amendment is fully executed. Any
      improvements other than those described above must be approved by the
      Landlord and shall be completed at the sole cost of the Lessee.

      Except as herein above set forth, all terms, provisions and covenants of
the Lease shall remain unchanged and in full force and effect.

      IN WITNESS WHEREOF, the parties hereto have executed this Amendment #4 as
of the date and year first above written.

Lessee:                                   Landlord:
STRATASYS, INC.                           CARPENTER LAND COMPANY, L.L.P.
(a Delaware corporation)

By:  /s/ Donald Moffatt                   By: /s/ Judd Q. Carpenter
   --------------------------                ------------------------

Its: Chief Operating Officer              Its: General Partner
   --------------------------                ------------------------     
                                          

                                          By: /s/ Ann C. Kenny
                                             ------------------------

                                          Its: General Partner
                                             ------------------------