Check the listing for details. OS 61 SF Bearings (later model). Condition: New. Listed at 7.97 USD. OS 61 SF Stainless Steel Bearings (Later Model). These have a high speed plastic retainer from Japan in the rear bearing. NOTE: These rc bearings are appropriate for Heli engines. All heli engines. 40ci and above should use a rear bearing with a high speed plastic retainer!