The DISCOVERY HAMMER SPRING is the newer version Crosman started using around 2017. It's shorter and stiffer than the original. It produces a more consistent shot string with less hammer bounce. It's about 1-5/8" long with a wire diameter of .042". The older version is obsolete and no longer available.

 The 22XX HAMMER SPRING is original to 2240, 2250, 2260, 2300KT, 2400KT and similar models. It's stronger than the 2300T and 2300S version.

 The 13XX HAMMER SPRING is original to 1377, 1322, 2289G Backpacker, PC77 and 1300KT. It is not compatible with older 1377 and 1322 models with a pull-knob cocking assembly and sliding breech cover.