Sizing/Measuring Loc-Line Hose All Loc-Line hose systems are measured by the smallest diameter hole through the part. The smallest hole through the 1/4″ Hose will will be 1/4″ diameter.The largest outside diameter is approximately 5/8″. The smallest hole through the 1/2″ Hose will will be 1/2″diameter.The largest outside diameter is approximately 1″. The smallest hole through the 3/4″ Hose will will be 3/4″diameter.The largest outside diameter is approximately 1-1/4″. The smallest hole through the 2-1/2″ Hose will will be 2-1/2″diameter.The largest outside diameter is approximately 2-7/8″.