Great drop in frt - The Triggered Company Partisan Disruptor AR-15 FRT 3 Position Drop In Forced Reset Rifle Trigger w/ Single Side Safety Selector

Recommend just get a legit H3 dead-blow type buffer, use your standard carbine spring, nothing more fancy than that is needed per my experience. Played with H2 buffer, with mixed results, using H3 buffer and std. carbine spring, this has performed 100% with 10.5", 12.5" and 16" 5.56 bbls using Tula .223 and PMC X-TAC 55gr. Did not like a Adams Arms piston equipped 12.5" upper(excellent upper btw), probably need to spend time tuning it, but again works 100% on other DI uppers. Purchased several of the FRTs. Selector has 2 sharp edges/corners near the rotational axis, wears on your finger and/or gloves, easy fix with a file or dremel tool though, just a little rounding and its perfecto.