I bought this one for my cag mre recce build, the traditional FSB could block sight pictures when using the LPVO at ~1-2x magnification. However, I am not a big fan of the PRI-style folding front sight or m16 low-profile gas block. Therefore, this is the best I can find on the market. It fit all of my barrels and doesn't require an FSB cut on the barrel, and it stays tight on my GHK GBB. I will definitely purchase one more for my mk12mod0 build