This fitting is a push in fitting so you just push the line in from both sides. It is mainly used where a stronger connection is required on a rigid port.One side is a standard 8mm (5/16) duotight push in fitting, where the other side is a compression adapted duotight (Screw Lock)I can be used on any 8mm OD tubing. For example on an 8mm stainless steel tubing on a G40.1 Glycol Chiller.Or on an oxygenation wand / carbonation wand.This fitting also comes in a 1/4" (6.35mm) reducer down to 8mm Screwlock.duotight - 6.35mm (1/4) Screwlock x 8mm (5/16) - Reducer Elbow