uxcell Plastic Aquarium 3 Way Cross Shape Pump Air Valves Splitter Tube Connector 4 Pcs Gray They are made of good quality white plastic, non-toxic and durable It is suitable for connecting standard aquarium tubing, mending or extending air hose OutletDia(Each) : 4mm/ 0.2"; Overall Size : 42 x 37 x 12mm / 1.7" x 1.5" x 0.5"(L*W*D) Thread Diameter : 9mm/ 0.35"