39mm. Fits '87-later XL (except XL883N, XL1200N, XL1200X and '11-later XL1200C), '91-'05 Dyna (except FXDWG) and FXR models (except FXRT) with 39mm front forks. (Does not fit with Chrome Fork Sliders.) This Chrome Fork Brace is machined from billet aluminum, then polished and chrome-plated. Easy to install, this brace offers increased torsional rigidity.