Specifically designed to work with the Ultra Limited and Electra Glide Ultra Fork Spring Kits soak up the small road bumps, yet are firm enough to absorb the molar-rattling ones Spring rates have been chosen to reduce front end dive during braking, yet still provide excellent ride comfort Progressive Rate Spring has the advantage of a rising rate resistance to compression. Benefit of this is that the spring can be soft enough at the start of the travel to offer a plush ride, yet be firm enough at the end of the travel to soak up the big bumps Progressive covers these springs for life