The magnifier is on AP's twist/flip mount. I like how easy it is to remove the magnifier over other methods. I also recently purchased a PVS-14 and a mount to the twist mount. So it's pulling double duty.
I've run the Comp M4 with the front of the optic at the front of the receiver with the magnifier pushed further back (and no rear iron) on my M4A1 with the guard; which I do not like the eye relief or added weight of the combined magnifier and red dot, but the addition of the magnifier is an awesome add-on. I can knock off 6 oz in the optic alone going from M4S to M5S and I can throw the M4S on a future purchase.