Everything you need for your custom build, and nothing you don't.  Just the basics from KAK.
Features :
       Features :
- Bolt Catch Kit
 - Magazine Catch Kit
 - Takedown Pin/Detent/Spring
 - Pivot Pin/Detent/Spring
 - Buffer Retainer Pin/Spring
 - Ambi Selector/Detent/Spring
 - Hammer and Trigger Pins
 - Hammer/Trigger/Disconnect Spring
 - De-Grease Ambi Selector Screw Threads and Apply Blue Loctite When Assembling