I had a spitfire 3x, bought it because the dealer said it was night vision compatible, but nope they aren't. I used it a little bit but had it mounted forward on my rail to use with the PVS. I sold it to a buddy, but I really liked it for anything out to about 200 yards worked great. If I would have had another upper to have used it on I would have kept it. No experience with the primary arms for comparison though.