Does this drop in (like ASA) or use set scews or?

Goes in from the bottom, uses a Allen that locks it in...Having said that...Mine wouldn't stay in place to save its life,Keep riding up into the bolt carrier no matter how tight I made it.Ended up pinning mine in from the front behind the takedown pin so you cant see it,..On the plus side it has a functional hold open(if you use colt mags)and the magwell is a little looser than the ASA's(from what I hear)so you cant use just about any mags..I found the SA "colt" mags work best for me. there snug in the magwell and taper up to a single feed and are the only mags I have that will chamber hollowpoints without ramp or chamber mods.The uzi's are loose in my mags well...I hear that the ASA blocks only fit IMI Uzi mag's, and that even "contract" mags are too tight....UNDERDOG