General Hydroponics 1/2" I.D. Rubber Grommet for Barbed fittings (Pack of 4) 1/2" Inner Diameter Rubber Grommet by General Hydroponics Forms a watertight seal with 1/2" barbed fittings Perfect for hydroponic and water based applications Thicker and strongers than regular rubber grommets 1/2 inch rubber grommets are easy to find fittings for