The HK VP9/P30/USP9T 9mm M13.5×1 LH Thread Cap is a protective accessory designed to fit over a firearm’s threaded barrel when a muzzle device (such as a compensator or suppressor) is not installed. Machined to the M13.5×1 left-hand thread specification, this cap helps shield the barrel threads from damage, debris, and corrosion during transport, storage, or shooting without an attached device. Built to complement compatible Heckler & Koch 9 mm platforms such as the VP9, P30, and USP9T, it provides a simple solution for maintaining thread integrity and overall barrel condition.