The Meprolight M21 reflex sight is by no means the latest or greatest, but it’s rugged and performs well (which may be why the Israeli Defense Force adopted its use en masse). Read up.
Mike Kupari is a former Explosive Ordnance Tech and GWOT veteran who spent several years as a PSC contractor at home and a PMC contractor abroad. He is a successful novelist and prolific freelancer, having written for a number of gun/tactical industry publications. Mike's previous books include the bestselling Dead Six series (co-authored with Larry Correia), a sci-fi series (Privateer Andromeda), and his most recent yarn, a post-apocalyptic tale called The Family Business. You can find his novels at Baen Books or online at Amazon.com.