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.Features :Gen 5 Specific and Not Compatible with any other GensAll Parts are from US ManufacturerParts are Made to the Highest Tolerance to the Original SpecificationZP Stainless Steel Recoil Spring Assembly-OEM Spring Weight