Hi K Youn,
Thank you for inquiring with IndeMedical.com!
The included 18" extension tube connects a Foley or External Catheter to the Leg Bag at the top of the bag. The leg bag utilizes a stepped plastic connector which the extension tube fits over.
Please call 480-704-3807 if you need additional instruction.
Thanks,
Mike Benge
IndeMedical.com
480-704-3807