A usable rear a2 sight at a decent price - Luth-AR A2 Rear Sight Kit

This sight comes completely disassembled, so one should be careful, especially with the detent balls, as they can be easily lost (using grease helps to keep them in place). This rear sight is not as tight to the receiver as the one from RRA, but it is cheaper, so as the sight goes up and down it turns ever so slightly with respect to the receiver, and when it is almost all the way down, one can rotate it a bit by hand. I know this doesn't impact accuracy, but it feels less solid.