It fits perfectly - Faxon Firearms 3 Screw AR-10 Gas Block

I purchased this for an AR10 pistol along with a pistol length gas block. I did however forget to order a roll pin. Luckily I was able to borrow one from an ar15 block I had. My recommendation is to remember the roll pin. The standard AR-15 gas block roll pin is 5/64" x 5/16", though some manufacturers may use a slightly longer pin for added security. For a low-profile gas block, a shorter pin like 5/64" x 1/4" might be used. It is always best to check the specifications of your specific gas block.