I went on a vacation this past week, and returned home to find my block had arrived. I punched out the pins, and installed the new block. The set screws make it easier than putting on an A2 sight. I have installed railed blocks before, and just didn't understand why they wanted me to send in the upper. The rep said that they had seen several butchered rifles from people not installing the block properly. I did get an e-mail back now, that said I did not need to get a smith, aor send it in , and gave very good info. I guess someone thought they could make a few bucks by me sending the rifle in. Anyway, the block/sight is on and looks and works great.