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.
