Precision Double I/D Air-cushion inner barrel by TNT Airsoft.
The TNT barrels are an unusual but effective barrel that starts out at 6.03mm and expands out to 6.35mm with specialised channels cut into the last section.
The idea behind this is to reduce the pressure behind the BB and allow more air to pass over and in front of the BB, creating a stabilising effect.
TNT Airsoft barrels are a great drop in part and work well with a variety of bucking.
Material : bronze with electroplated chemical nickel surface.
Inside diameter : 6.03~6.35mm (different inner diameter in barrel)
Outside diameter : 8.5mm