This is a custom NYLON compound gear for the 10" and 12" Atlas/Craftsman metal lathes.   This gear allows gearing down the feedrate to 1/2 what is shown on the quick change gearbox for extra fine surface finish.  It is a DP16 gear with 48 teeth and 24 teeth.   This gear has the double keyway for the Atlas gear shaft as shown with a 3/4" shaft bore and two 3/16" keyways.  This keyed connection helps ensure the gears do not break free from each other even after extended or hard use.  The gear is made of Nylon with a proper involute gear tooth profile that works and meshes very well with the original Zamak gears used on these lathes.

Don't bother buying PLA (red), ABS, Carbon Fiber gears as they will simply not hold up as well as Nylon.  They do last a short while if you only need a few cuts but they will not last like these nearly solid Nylon gears.  I've been using a similar Nylon gear for several years without any signs of damage.  See my other ebay items for other Nylon gears and parts.

Note: Part may be white, grey, or black Nylon, all have similar properties.