picked one up used and put it on an ARMS #19 mount  for my M4 flat top (14.5 inch bbl)

took it to the range and it worked awsome
clear optics & light weight
Its like the old Colt 4 power scopes that mount on the A2 but has a built in weaver rail
has bullet drop comp for 100 to 600 yrds and finger adjustable windage
quick detach and change between my Aimpoint red dot and C-more 4x scope using ARMs mounts

at 50 yrds I was keeping my groups at 1 inch (max 2 inches) with olympic 55gr ammo resting mag on bench - no bipod

highly recommend getting them if you can find them
if anyone knows where to get more let me know I may buy 1 or 2 more for other rifles