| '''Old style''' || Optics: N/A || [[Colt AR-15A2 R6550]]<br/>[[Colt M16A1]]<br/>[[Colt M16A2]]<br/>[[Colt XM177E2 Commando]] || '''200''' || Original style upper receiver with non-detachable carrying handle, and no mounting points for optics.
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| '''Flat top''' || Optics: NATO-S mount<br/>(or '''NATO mount''' if the '''Quad rails''' are also installed) || [[Alexander Arms AWS]]<br/>[[Colt M16A4]]<br/>[[Colt M4]]<br/>[[Colt M4A1]]<br/>[[Colt Mark 18 Mod 0]] || '''600''' || Modern upper receiver with a length of NATO-S rail for mounting optics. Comes with a detachable carrying handle with adjustable rear iron sights.<br/>If paired with the quad rails, the top rail section serves as an extension of your flat top, giving you a full-length NATO rail.
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| '''DMR''' || Optics: Integrated 3x scope<br/>Affects weapon category<sup>'''[[Maze Customs:Major mods#AR-15 weapon categorization|(*)]]''' || || '''600''' || Special upper receiver featuring a proprietary ART II 3x scope, in the style of the Colt Model 656.