Sets over tighten and lost exhaust nuts an end. The grooved mutter can be tighten to the correct specification, then a special washer goes over it and will be secured with a clip. Now it is impossible for the nut to be open without removing clip and washer.
Fits all aircooled Buell, S1 - M2 - S3 - X1 - XB and all Sportster since 1991 till today
Comes as a set of 4 for one engine.