FKS 517 FORK CARTRIDGE OHLINS HARLEY DAVIDSON FXDR-114 2021 NIX 30 Street Comments are closed Damp tech: NIX 30. Upgrade the comfort and performance of your Harley-Davidson with the? . Each fork leg features an 8-mm steel shaft, an aluminum damper tube, and 25-mm pistons, greatly reducing the dreaded brake dive.