Non Printed Parts:

2 AR buffer castle nuts
AR Milspec Buffer tube
AR buffer tube end plate (lock plate)

Assembly:

End plate and one nut goes on tube threaded as far as possible. 
Insert tube through hole scre as much as you can of inside nut on. 
Pull into grooved slot, screw in tube until end of tube is flush with second nut. 
Align end plate and tighten down outside nut.