Comparison : Item # 31128, 1/2 Inch (in) Nominal Inside Diameter (ID) Flange
Item # 31129, 3/4 Inch (in) Nominal Inside Diameter (ID) Flange
Item # 31130, 1 Inch (in) Nominal Inside Diameter (ID) Flange
Item # 31131, 1-1/4 Inch (in) Nominal Inside Diameter (ID) Flange
Item # 31132, 1-1/2 Inch (in) Nominal Inside Diameter (ID) Flange