Upper Parts Kit (UPK) for Glock 19 Gen 4. These are great for completing your custom slide. All parts are from US manufacturer. All Parts are made to the highest tolerance to the original specification. Warning: This product is to be installed by a competent gunsmith. No liability is expressed or implied for damage or injury which may result from installation or use of this product.image Firing Pin Spring Firing Pin Spacer Sleeve Spring Cups (2-Pack) Firing Pin Safety Nitride Firing Pin Safety Spring Extractor Depressor Plunger Nitride Extractor Depressor Plunger Spring Spring Loaded Bearing Firing Pin Channel Liner Extractor Slide Cover Plate Aluminum Recoil Spring Assembly