SureLok Fittings are recommended for compressed air as a connector on all air brake systems. Not for use between chassis frame and axle or between towed and towing vehicle. Also as a connector on all air operated systems as applicable to suspension, steering, engine, transmission and auxiliary mechanisms. Fittings and tubing comply to Department of Transportation Federal Motor Vehicle Safety Standard (DOT FMVSS 106) mandatory requirements for inch tube fittings in U.S.A. Society for Automotive Engineers (SAE) J1131 (inch tube and fittings) and meet DIN 74324 for German TUV requirements (metric tube and fittings).