DG Performance 23-91250 - 2.5" dia.Universal Bolt-On Steel Silencer - Black fits Universal 1 1/4" ID. Bolt-On Steel Silen (All - All) Suitable for older motorcycles and custom applications 1 fits most 100/125cc bikes, 11/8 fits most 250cc bikes and 11/4 fits most larger bikes Measurement is the inside diameter of inlet