ALG Defense Lower Parts Kit w/ACT Trigger. This kit 16-001 comes with: Bolt Catch Bolt Catch Plunger Bolt Catch Spring Bolt Catch Roll Pin Mag Release Mag Release Button Mag Release Spring Buffer Retainer Spring Safety Buffer Retainer Safety Detent Spring Safety Detent Trigger Guard Trigger Guard Roll Pin Takedown Detent SpringsTakedown DetentsTakedown Pins QMS Trigger This kit 16-002 comes with: Grip Grip Screw Washer Grip Screw Bolt Catch Bolt Catch Plunger Bolt Catch Spring Bolt Catch Roll Pin Mag Release Mag Release Button Mag Release Spring Buffer Retainer Spring Safety Buffer Retainer Safety Detent Spring Safety Detent Trigger Guard Trigger Guard Roll Pin Takedown Detent SpringsTakedown DetentsTakedown Pins QMS Trigger This kit 16-003 comes with: Bolt Catch Bolt Catch Plunger Bolt Catch Spring Bolt Catch Roll Pin Mag Release Mag Release Button Mag Release Spring Buffer Retainer Spring Safety Buffer Retainer Safety Detent Spring Safety Detent Trigger Guard Trigger Guard Roll Pin Takedown Detent SpringsTakedown DetentsTakedown Pins ACT Trigger This kit 16-004 comes with: Grip Grip Screw Washer Grip Screw Bolt Catch Bolt Catch Plunger Bolt Catch Spring Bolt Catch Roll Pin Mag Release Mag Release Button Mag Release Spring Buffer Retainer Spring Safety Buffer Retainer Safety Detent Spring Safety Detent Trigger Guard Trigger Guard Roll Pin Takedown Detent SpringsTakedown DetentsTakedown Pins ACT Trigger Specifications for ALG Defense AR15-M4 Mil-Spec Lower Parts Kits: Manufacturer: ALG Defense Gun Make: AR Platform Gun Model: AR-15 Package Contents: ALG Defense AR15-M4 Mil-Spec Lower Parts Kits ALG Defense 16-003: Lower Parts Kit w/ACT Trigger