1) Remove factory basepad and retainer plate. To add NO ADDITIONAL CAPACITY to the magazine skip to step 3
Remove magazine spring and slide factory follower down to base of
magazine so that the load assist pin can be removed from the follower.
Compress spring into magazine body and slide on the aluminum basepad.
Assure that the spring is in the pocket of the basepad.
4) Finger tighten set screw with the included hex wrench.
Sig Sauer 22 Mosquito High Capacity Magazine