Specially hardened steel wheels meet ANSI B30.11 specifications (Certificate included)Load is moved by pulling on hoist load chain in direction of travelDouble sealed ball bearings for long lifeSpecially designed integrated drop stops/bumpers take the load in the event of wheel failure and prevent wheels from contacting other trolleys on the trackAdjustable to fit various sizes of flanges and beamsComes equipped for use on up to 8" beam widths