39mm Solid Riser Bushings - Raw Aluminum Counterbore aluminum riser bushings fit 39mm narrow glide front ends and replace the stock rubber bushings and washers. Ideal for those who want solid-mounted handlebars or for use with tall handlebars for added rigidity and stability. Featuring a counterbore for your allen cap hardware on the underside resulting in a flush mount, cleaning up the underside of the top triple tree