Designed to replace Harken rudder bearings. Many J-boat, including the J-120 are due for major rudder bearing service or replacement. These bearing fit without modification to the boat. J-120 Lower Bearing- Large ID roller bearing. The bearing is shipped with a stainless steel sleeve to bond to the rudderpost. The sleeve is the same height as the stock unit. You will need to keep the existing sealing system in place. OD=8.49", Height=2.75", Sleeve height=9".