Right fitting 3/8 Thread O-ring - 8 mm tube

FITTING 3/8 INCH SINGLE THREAD BSPP O-RING - TUBE 8MM - 5/16 INCH

8 mm quick fitting with O-ring to screw on arrival or exit drinking water 12/17 or 3/8 inch.

His O-ring gives him the advantage of making the hermétque union, thus avoiding the risk of leakage.
It connects to all types of filtration devices, or other equipment requiring circulating water, air or gas.
The quick connector side 8mm round receives many flexible or rigid tubes without extra room needed.
For the flexible tube 5/16 inch (8 mm), it must be pushed to the bottom of the quick release.

Food Standards FDA - NSF.