Check the listing for details. Progressive Front Fork Lowering Kit 1in 49mm Tri Glide Ultra Classic 17-18. Condition: New. Listed at 166.58 USD. Take control of your ride with a Progressive Fork Lowering Kit. This kit is designed to provide a comfortable ride, no matter the terrain. It comes with springs and spacers that are progressively wound to offer more comfort and control even over rough roads. Installation is easy, as detailed instructions are included with the kit. The progressive winding makes this kit different from others you may have seen out there; it offers superior absorption over bumps and unevenness on the road. With these components in place, your bike will become easier to handle and much more stable with every ride. Every rider should have the assurance of a smooth, comfortable ride that adds confidence and pleasure to their journeys.