Progressive Drop-In Fork Lowering Kit For Harley Sportster Features: These kits, when combined with shorter than stock rear shocks, will give you that low, custom look Comes complete with Fork Springs, spacers, and instructions. Spring rates have been chosen to reduce front end dive during braking, yet still provide excellent ride comfort Lifetime fork springs warranty Progressive Rate Fork Springs have several advantages over straight rate springs, advantage of a rising rate resistance to compression this helps in varying road conditions from small road imperfections to pothole filled roads