I am looking at getting a EOTech and i was looking on primary arms, and they offer combos with there 3x mag and mount for it, i was just wanting to know which flip to the side mount i would need to get absolute co-witness with my mbus sites if the EOTech is mounted on the flat top rail. they offer standard 1.6 inches above the top mounting rail and tall 1.75 inches above the top mounting rail. This will be going on a M&P15 T

measure from the top of the rail to the centerline of the sights, it should be able to give you the information you need!!

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Grover Oathkeeper