The Valken 6.05mm Anodized Inner Barrel is an airsoft internal spare part for airsoft AEG rifles. This AEG inner barrel is 381mm long, and is a factory replacement part for the Valken ASL+ Hi-Velocity Whiskey AEG Rifle. This airsoft inner barrel can also be used in other compatible AEGs and other rifles using standard AEG specification inner barrels. To determine the length you need, measure from where the magazine feeds the airsoft BB to the tip of your inner barrel, or where you want your inner barrel to end. Subtract ~5mm for hop-up unit. Remember that it is perfectly okay to have an inner barrel shorter than your outer barrel, or have the exposed sections hidden in a longer flash hider or mock silencer.