My next project is to make Ariel rocker caps and Burman gearbox oil filler caps. I plan to machine these from Fortal round stock. Both of these items have become very hard to obtain. The original components are cast from some gray alloy which is pretty much impossible to polish, and the casting method of manufacture leaves the hex flats slightly slanted, making them very easy to round off. Fortal is strong, polishable and machining should give accurate hexes.