Progressive Heavy Duty Fork Spring Kit For Harley-Davidson 49mm ForkProgressive Heavy Duty Fork Spring Kit For Harley Davidson 49mm ForkDyna and V Rod The 49mm fork is a significant upgrade from the 39mm unit it replaced, but when pushed hard when touring or if routinely riding with a pillion, some riders may need improvement. Progressive has a solution. Heavy duty version of Progressive Suspension's progressively wound fork springs Cost effective yet substantial increase in front end ride quality Kit includes