6" x 2" V-Groove Cast Kingpinless Swivel Caster Med Heavy Duty,1000# Cap6" x 2" V Groove Cast Iron Wheel Kingpinless Swivel Caster Cast iron v groove wheels are made for use with inverted angle track but they can also be used to roll on floor tracks, gate fence tracks and flat surfaces. Constructed of cast iron with a 90 v groove, this wheel works well inside and outdoors. Tread: Solid Cast Iron 90 V Groove Core: Solid Cast Iron Bearing: Roller Bearing Rig: Kingpinless zinc plated swivel caster, 4" x 4 1 2" mounting plate