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.
https://shop.bitspower.com/index.php?route=product/product&product_id=3961&search=-CPF-CC3U
