PM has created a new 4-piston billet aluminum caliper specifically engineered for 2008-19 FLHR, FLHRC, FLHX, FLHT, FLHTC and FLHCU, 2014-19 XL, 2015-17 FLST,FXSB, 2006-17 VRSCDX, VRSCD and VRSCAW utilizing the stock brake master cylinde These Harley models utilize a smaller 15mm bore in the brake master cylinder which requires the use of a smaller volume caliper This PM 4-piston caliper uses PM's proven caliper design standards to optimize the braking performance on these specific HD models