RCD crank hubs are machined from American sourced heat-treated chrome-moly billet steel or titanium. Each hub has six evenly spaced 3/8-24 or 7/16-20 threaded holes with a stepped profile for weight reduction and to lock-on a degree ring. Most hubs have two keyways machined 180 degrees apart. RCD also offers hubs with an internal spline which provides greater driving concentricity and eliminates keyway galling. All steel hubs are provided a black oxide finish to avoid corrosion. RCD has created several custom hubs for our customers over the years, if you can't find what you need call to configure a hub to fit your application.