Lol...if you're going Mod 0, you'll need a ARMS #38 SPR PEQ2-3, AKA Swan sleeve, AKA SEX sleeve...the full length optic riser that bridges the gap between the upper receiver and the rail...
Are y’all even speaking English right now?!
Oh no I'm going Mod 1. I need A.R.M.S. #22 High rings IIRC