Rob Allen Tuna SpeargunRob Allen aluminium railbarrels have the same dimension as the carbon barrels. The rail level lines up with the profile of the mechanism and the muzzle. The integral rail is part of the barrel, thus increasing stiffness and reducing flex. This makes the guns deadly accurate. The rail barrel is manufactured from aircraft grade aluminium with a wall thickness of 1. 45mm and the mechanism is manufactured from glass reinforced nylon and has a solid 316