Hello GVJ,
Both sides of BP-CBE90DML16-TB only can connect with OD16 mm hard tubes.
If you want to connect with the fitting, you can choose BP-CB90DIG14 or BP-TB90DIG14, which both sides can connect with the fitting has G1/4" thread.
https://shop.bitspower.com/index.php?route=product/product&product_id=970&search=90DIG14