Black Washers - 3/8 ID x 7/8 OD (10)

The Black Washers - 3/8 ID x 7/8 OD (10) from ARP represent a critical fastening component trusted in demanding tactical, military, and precision firearms applications. These hardened steel washers distribute clamping load evenly across threaded assemblies, preventing component creep and maintaining zero retention under recoil and sustained use. Available in a 10-pack configuration, they address the real-world need for redundancy and replacement inventory—critical when field-stripping equipment or performing maintenance on mission-critical platforms.

Manufactured to ARP specification 200-8688, these washers feature a 3/8-inch inner diameter and 7/8-inch outer diameter, engineered to mate with standard 3/8-inch fasteners while providing maximum surface contact area against receiver flats or rail systems. The black oxide finish resists corrosion in harsh environments—salt spray, moisture, and prolonged storage—while eliminating light reflection common with bare steel. This material composition ensures washers remain stable across thermal cycling and high-pressure environments, critical for bolt carrier group assemblies, rail systems, or optic mounting interfaces where vibration-induced loosening would compromise accuracy or weapon reliability.

Law enforcement, military armorers, and precision rifle builders standardize on ARP washers for upper and lower receiver assembly, furniture attachment, and accessory rail installation. The 10-pack supply supports both initial builds and maintenance cycles, ensuring you maintain spare inventory for field repairs or platform rebuilds. Compatibility spans AR-platform rifles, precision bolt actions, and any tactical system utilizing 3/8-inch fastener assemblies where load distribution and vibration resistance are non-negotiable.