You small parts will do fine

by Miles , CIVITATES AMERICAE, Monday, April 13, 2015, 23:06 (3452 days ago) @ rob
edited by Miles, Monday, April 13, 2015, 23:13

And, you'll like the Geissele trigger.
Just make sure you follow the installation directions.
And make sure you really practice with it because it is not like any standard trigger you've ever shot.

There's not really much difference in the quality, just the size between a .mil, or a 'commercial' receiver extension (buffer tube). It's just how they are made.

Personally, I'd get the military size tube and buttstock. but that's just "me".