Comstock Armory RPA HUB Recessed Plan-B Suppressor Adapter, Stainless Steel The Comstock Armory RPA-B-SS is a recessed Plan-B suppressor adapter for compatible 1.375-24 HUB/Bravo rear interfaces. Its 17-4 PH stainless-steel body and black nitride finish provide a steel mounting option in a 2.1-ounce package. The recessed profile places a compatible muzzle device 0.40 inch deeper than the standard Comstock LPA. This can shorten the assembled system and tighten the handguard-to-suppressor gap, but it also makes available blast-chamber clearance a central fitment requirement. Shop the Comstock Armory steel RPA at BattleHawk Armory for your compatible HUB suppressor. Recessed Profile and Clearance The RPA adds 0.18 inch of adapter length while bringing the muzzle device farther into the suppressor. Added adapter length and the change in muzzle-device position describe different dimensions. Confirm both the muzzle device's length and the suppressor's available internal clearance before choosing a recessed adapter. Steel Body and Dual Tool Interfaces The body is machined from 17-4 PH stainless steel and receives a black nitride surface treatment. A 1-7/16-inch wrench interface and 1.5-inch spanner notches provide two defined tool interfaces for servicing the adapter. These dimensions refer to the adapter and should not be confused with the muzzle device's wrench size. HUB and Plan-B Compatibility The suppressor connection uses 1.375-24 HUB/Bravo threads. The muzzle-device side accepts compatible Comstock, Rearden and other Plan-B-pattern devices. Neither interface alone guarantees that the assembled parts have enough internal or handguard clearance. Confirm the exact suppressor, muzzle device and barrel combination, including the suppressor's cartridge rating. Product Specifications Manufacturer: Comstock Armory Model / Manufacturer SKU: RPA-B-SS UPC: 850069580285 Product type: RPA HUB Suppressor Adapter Material: 17-4 PH stainless steel Finish: Black nitride Weight: 2.1 oz Suppressor interface: 1.375-24 HUB/Bravo Mounting system: Plan-B pattern; complete-system fitment required Added length: 0.18 inches Frequently Asked Questions How much farther does the muzzle device extend into the suppressor?The recessed RPA positions the muzzle device 0.40 inch deeper than the standard Comstock LPA. Available blast-chamber depth must accommodate that position. What tools fit the adapter?The adapter has 1-7/16-inch wrench flats and 1.5-inch spanner notches. Follow the component manufacturers' service instructions. Does HUB threading guarantee compatibility?No. The matching rear interface is one requirement. Muzzle-device fit, internal clearance and complete-system compatibility must also be confirmed. Choose the Comstock Armory RPA-B-SS at BattleHawk Armory for a recessed steel Plan-B interface with clearly defined HUB fitment.