An actual slick side upper - Aero Precision AR15 Assembled Upper Receiver, No Forward Assist

A lot of slick side uppers (cough cough KE) are actually made off of FWA blank uppers that simply never had the hole milled out for the FWA. Not this one. This one is a real slick side, which means it's smoother, more rounded, weighs less, and is better overall. So far I've bought 3 of these slick sides for different builds, and the quality is impeccable on every single one. I cannot recommend this part enough.