Gas cylinder filling connection according to DIN 477 W 28,8 X 1,814. Pressure ramp accessorie. It make the air possible to leave the cylinder. You could check if the cylinder is already full or not. It could circulate the water without loss.
The product make us possible to fill water into gas cylinders with 25E threads. It is not pressure proofe! It is not approved for high pressure testing!. It could be used only filling. During filling it let the air out of the cylinder. You could check if the gas cylinder already full or not.