The 5KU Tokyo Marui Hi-capa 5.1 aluminum outer barrel is made of aluminum. The barrel is designed to fit the Tokyo Marui Hi-Capa 5.1 series airsoft gas pistols. This barrel has an 11mm CW female thread at the end, which allows you to easily add 11mm internal thread accessories or a 14mm CCW suppressor adapter to your airsoft pistol.
