Push Fit Airline Brake Fittings
Brand New Genuine John Guest Speedfit Metric Black Acetal Push-In Fittings

No tools required for assembly. Easy to connect. Include a food-grade nitrile O-ring. Compatible with nonbraided PVC tube, polyethylene, nylon, polyurethane, brass, copper, and mild steel tubing. 
Use for compressed air.
Max. pressure: 150 psi (10 BAR) 

Genuine John Guest - Reducing Straight Connector (1/4" x 3/16", 5/16" x 5/32", 5/16" x 1/4", 3/8" x 3/16", 3/8" x 1/4", 3/8" x 5/16", 1/2" x 5/16", 1/2" x 3/8")

Delivery time in UK is 4-6 working days.