Air brake line fittings types: 1/8″, 1/4″, 3/8″, 1/2″. 64 Pcs Brass DOT Air Line Fittings Kit Push Lock & Quick Connect Fittings NPT Thread for Air Line Air Hose Pneumatic Tubing. EASY INSTALLATION: The quick connect design and precise NPT threading make installation of air brake accessories easy, just push to connect.