Biltwell Thunder Risers For Harley Features A large number of late-model Harley owners who prefer tall handlebars convinced Biltwell Inc. to develop the Thunder risers The one-piece design increases riser stiffness and clamping power on rubber-mounted top trees, and is a boost to performance and style on practically any motorcycle Investment-cast and CNC-machined stainless steel 5/16 x 18 t.p.i. stainless steel bar clamp hardware This one-piece riser fits rigid and rubber-mounted top trees with 3-1/2 (89mm) center-to-center mounting holes only (Wide Glide, Narrow Glide, H-D aftermarket trees, etc.) If your top tree has different mounting holes, Thunder risers will not fit your motorcycle Also, the holes on your trees must accept 1/2 O.d. hardware The lower clamp is threaded to accept 1/2-13 mounting hardware (not included) Risers accept 1 bars