Only The Custom Defiance Knee Brace has a serial number. The Full force ligament knee Brace does have the size printed on the inside of the liner that is on the top of the thigh cuff. Pull it back from the frame and the side and size should be printed on it.
The Full Force comes with one Supra condylar Pad and one suede pad. Copy and paste these links
Will this set ( FullForce Strap Kit) be the right one for my Difiance Brace No. P1023-10600 ?
You will need this kit for your Defiance: https://www.donjoystore.com/donjoy-defiance-custom-replacement-straps-and-pads-kit You will need that serial number to order the correct size