Upper Parts Kit (UPK) for Glock 17 - Gen 5. These are great for completing your custom slide. Includes Firing Pin Spring and Pin Spacer Sleeve, Spring Cups, Firing Pin Safety Nitride and Spring, Extractor Depressor Plunger Nitride and Spring, Spring Loaded Bearing, Firing Pin Channel Liner, Extractor, Slide Cover Plate, Upgraded ZP Stainless Steel Recoil Spring Assembly.