Fits Ø2.0 Fox shock with 5/8" shaft.
This is an adapter hose.
It has 1/8" NPT tapered thread one end and parallel 7/16" UNF O'ring boss the other.
Used to connect new type reservoirs to older type shocks or vice versa.
Fox Ø2.0 x 5/8" Shaft Res Hose 12" (-5 1/8 NPT x 7/16-20 O' Ring Boss)