A tight fit, but works well otherwise - Vism Upper Receiver Block For Ar-15

Used it with a couple uppers, and it generally looks well. My only two complaints are that it was a bit snug, requiring some force to get it to slide inside the upper receiver, and marring the finish slightly on one. Also, the pins that engage with the takedown and pivot lugs are a bit undersized and loose, so they don't really do anything to secure the upper, but due to the design, they aren't really necessary, as the block is in two pieces that screw together and hold the upper securely even without the pins. Overall I would still recommend at this price point, and it does hold the upper securely, and works well for my use. Just be aware that you may need to grind down the back of it slightly to get it to slide in easily without marring the inside of the receiver.