CLAMPSThe following clamps are marked according to the I.D. (inside diameter) of the tubing being clamped. Cummins Onan drawings specify “to fit a specific diameter,” inch which is the O.D. (outside diameter) of the tubing. These two numbers differ by 1/8".A=Tube O.D.; B=Tube I.D.; C=Clamp Stamped: A=1-1/2"; B=1-3/8"; C=1-3/8" MFG# 155-1015 1551015