Quick explanation from Wes at Cross Armory about what a Slide Lock Spring is and how to put it in! This spring goes under the slide lock on Glock and 80% compatible pistols. This spring keeps the slide lock up and in place. Our spring is ground flat on each side to improve the firmament and to make installation easier. Fits all Gen 5 Glock frames and comparable 80% frames, except Glock 42/43/43X/48. Parts are available at Cross Armory . Com LINK – https://crossarmory.com/shop/slide-lo… Fits all Gen 5 Glock pistols Fits all p80 and 80% compatible with Gen 5 2 Pack Ground flat ends for improved fitment