That is a 46T Kyosho nylon spur gear. The Losi 8ight center diff cup is the same one that is used in the Muggy and Sportwerks 1/8 scale vehicles. The stock diff cup did need to be modified, in that I reduced the outside diameter of the upper portion of the cup by about 20/1000ths. It is my understanding that the Maximizer aluminum diff cup does fit the Kyosho spur without modification, but I haven't confirmed this myself.