X PRODUCTS Billet Machined Slab Side Upper The X Products billet machined Slab Side upper is minimilist perfection for the AR15. Designed with aesthetics and functionality in mind, the Slab Side Upper starts it's life as a block of 6061 aluminum and machined to it's current shape. Features include, widended ejection port to eject all AR15 calibers, M4 feedramps, anti rotation tabs (works with most aftermarket rail systems), and lightened M4 picatinny rails, finished in a Type 3 Hardcoat Anodizing. Based on military M16 M4 prints to ensure proper fit on any lower receiver, but minimalized to keep it clean. Perfect for the clean AR15 build.