Mainshaft support bearing in backside of inner primary cover. This is the outer roller bearing only, without the inner race, which is crimped onto the mainshaft. OEM replacement reference 9231. Note: See optional 921494 (34091-08) inner race for 08-up models. See optional 921493 (34091-06) inner race for earlier 06-07 Dyna; 2007 Softail; Touring models.