Its ok but not worth the price - XS Sight Systems Armorers Block for AR Platforms

The AR-15 uppers I have fit just fine in it for the lugs to line up with the holes in the block. However, the pins that it comes with the pin for the back fit just fine through the lug for the upper the pine for the front lug would not go through the upper lug hole I had to go to my farm supply store and find a pin that would go through the lug. My AR-10 upper is standard mil spec the front lug and pin fit just fine the block would not let the back lug go down far enough to line up with the pin hole as the upper was hitting the block just to the rear of the front pin hole.