Dear Customer,The internal diameter of BP-ETW is IG1/4".You can use any male adapter which has G1/4" thread.Such as our soft tubing fitting BP-CPF-CC3U.One side of BP-CPF-CC3U connects with BP-ETW, and the other side connects with ID 3/8" OD 5/8" Tube soft tubing.If you have any questions, feel free to contact us.
