You are purchasing a nice USA-Made reproduction of the knurled aluminum steering damper knob used on 1959 Sportser XLCH models and possibly racing models as well, check your own reference materials.  

My book says this is for 1959 only, but the knob was included in a 1962 and later NOS XLCH damper kit I've seen before.

This is a 5/16"-18 thread.

We sell many other parts for Panhead, Knucklehead, Sportster, Hummer & other lightweight, flathead, JD, VL, DL, RL, and single models including Solar and Motolamp headlamps, dash panels, ammeters, oil and fuel lines, and complete wiring kits.  If you don't see it there or cimarroncycleworks, just email us and ask.  We are starting to carry more parts for the early models and Sportsters, keep an eye on our space!

Located at and ships from Cimarron Cycle Works in beautiful Cimarron, New Mexico, USA! 

Used on the following model, please cross-check your own reference material to make sure this is right for you: