This is a scar barrel designed by Thanh for FDM printing, featuring his unique SCOBAC system. SCOBAC stands for Sliding Clutch Operated Barrel Attaching Clamp, which means you can install or remove this scar barrel on your Caliburn's barrel, or other 5/8ths OD barrel, without the use of tools. A printed scar barrel also means that you do not have to worry about strings, as the rifling is baked into the design.