The Castle nut for the Baja Reaction BR150 go-kart features an M12-1.25x12 thread.
A castle nut (short for "castellated nut") is usually used with threaded rods or bolts with a hole bored for a cotter pin. The pin fits through the hole and castellations to prevent the nut from turning until the pin is removed. This feature makes the castle nut a preferred fastener for axles, tie rods, shocks, and other components of the front suspension system.
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