Fits Atom models 205, 301, 310, 415, 420, 431, 435, 438, 440, 441, 450, 453, 454, 458, 480, 481, 505, 506, 550, 560, 561, 562, 580, 581, 581, 582, 585, 586, 601, 602, 650, 20205, 20301, 20310, 20415, 20420, 20431, 20435, 20438, 20440, 20441, 20450, 20453, 20454, 20458, 20480, 20481, 20505, 20506, 20550, 20560, 20561, 20562, 20580, 20581, 20581, 20582, 20585, 20586. 32 x 10 x 12 + 4mm. Stepped/Extended Inner Race