Glock Factory Part Magazine Catch Spring Fits All Glock EXCEPT 21SF Model. GLSP00280 (aka GLSP 39543) This is a Glock factory OEM original part for your Glock. Why settle for second best or a knock off when you can have the original factory replacement part? Brand new. This replacement part is a factory original from Glock. Factory replacement parts are manufactured to the exact same specifications and tolerances and use the same manufacturing materials as the original parts which guarantees excellent fit and reliable operation.