Tuning 1377 exhaust valve

If it's for the Transfer port the poly refrigerator line werqs very well for a T-port. A piece of macro line from the paintball addition would werq also. So, many things werq well if properly sized for the transfer port on these guns.

If you decide to go with some type of tubing stuff a dowel or rod of some sort in the tube and roll a razor knife on it to get a straight cut which you will need for a good seal.