Works if you know its limitations - JE Machine Tech AR-15 Vise Block Upper & Lower Combo

What are its limitations you ask. Well, it is made of plastic or some polymer material. The upper blocks are a bit flexible when torquing a barrel nut. It does work at reasonable torque specification. You may want to add a C style clamp at the top of the two sections so that it does not spread apart. It does not fit an A1 or A2 style upper with the carry handle. I was not paying attention to this when I purchased it. I used it on an A4 style upper first. So, I used the lower mag block for the carry handle uppers, and it worked without breaking off in the vise. It did flex a bit, but it got the job done. No complaints for the price paid.