Black Washers - 3/8 ID x 5/8 OD (2)

The Black Washers – 3/8 ID x 5/8 OD (2) from ARP are precision fastener components engineered for firearms assembly, tactical builds, and equipment maintenance. These hardened steel washers function as critical load-distribution elements in receiver assembly, bolt carrier group construction, and trigger mechanism setups where military-spec dimensional tolerances are non-negotiable. Whether you're building an AR platform, performing armorer-level maintenance, or assembling custom tactical configurations, these washers ensure proper fastener seating and prevent surface damage to critical components.

ARP's black oxide finish provides corrosion resistance and matches mil-spec receiver coloring for professional aesthetics. The 3/8-inch inner diameter accommodates standard 3/8-inch fasteners, while the 5/8-inch outer diameter delivers adequate bearing surface to distribute fastener pressure across receiver material without causing deformation or stress concentration. The two-pack quantity covers paired fastener points—a common requirement in bolt catch assemblies, safety lever installations, or dual-point attachment systems found on AR-15 and AR-10 platforms. The compact 0.04-pound weight and minimal profile ensure zero impact on firearm function or weight distribution.

Armorers, gunsmiths, and tactical end-users benefit most from having these washers on hand for build cycles and field repairs. Compatibility spans all receiver types that use 3/8-inch fasteners—including mil-spec lowers, matched upper assemblies, and aftermarket furniture installations. These washers prevent fastener pull-through on aluminum or composite receivers where overtightening could compromise structural integrity. Stock this component for maintenance kits, build workbenches, or replacement during component upgrades when precision fastener alignment is essential.