Lantac M-SPEC Upper Parts Kit (UPK) for AR15 style rifles. - Manufactured to the highest quality standards using correct materials heat treatments and finishes to comply with up to date military specifications. - Kit includes the following: - Bolt Catch Plunger - Bolt Catch Plunger Spring - Bolt Catch Roll Pin - Bolt Catch Set Screw (6-32 compatible with Lantac Aero and other lowers). 1/16th Allen Key Head - Buffer Retainer x2 - Buffer Retainer Spring x2 - Takedown Pin Detent x2 - Takedown Detent Spring x2 - Pivot Pin Detent x2 - Pivot Pin Detent Spring x2 - Trigger Pin x2 - Safety Selector Detent x2 - Safety Selector Detent Spring x2 - Lifetime Warranty. - Made in the USA.