Tomac was nice enough to let me borrow is RX30 - I am so used to an Eotech on my PS90 - that I just can't get used to a single dot (like the RX30 or an Aimpoint). For me, it takes longer to find, and I tend to move it more in CQC than I do with the larger EOtech reticle. Anyway - I think I will buy another EOtech for my MSAR - just a matter of the XPS or a 512/517 model. The XPS reportedly will co witnesses exactly - does the 512 cowitness exactly too, or does it 1/3 co witness. I did see that the 517 does the 1/3 cowitness - but apparently this is because of a built in riser. So, that should put the 512 and the XPS at the exact same height, correct? I found the stock MSAR optic to sit too low for me. I don't want to have the same issue if the XPS sits lower than a standard EOtech.... Wanna kill these ads? We can help!