Fit adm uic billet & m4e1 forged uppers perfectly - Obsidian Arms AR-15 Upper Receiver Vice Block

IMO this is the best HDPE style upper receiver vise block ive came across. Well made and machined and both uppers I installed it in fir perfectly and tight with very little movement. Supports upper at bottom near pins to the top where charging handle rides. Ive done 4 builds over the past few years and have accumulated alot of different vise blocks. This block plus the 5 others I own means I can do anything that needs to be done on a AR style rifle. 1)-Obsidian Arms HDPE Upper Receiver Vise Block 2)-PlastiX HDPE Picatinny Flat-Top Rail Vise Cover 3)-SquirrelDaddy HDPE Mag Well v3 Vise Block 4)-NCStar Alum. Lower Receiver Vise Block 5)-Midwest Ind. Steel Upper Receiver Reaction Rod (MI-URR) 6)-Carbon Polyomer Solutions Nylon/Carbonfiber Buffer Tube Vise Block. All but 1 of these vise blocks were affordable aside from the Midwest Ind. URR which I paid $90 for but its the only one ill use for barrel nuts & muzzel devices and it will also tell you if your barrel is clocked properly.