Aka, triple swivel caster, a wheel assembly designed to improve upon the traditional offset caster. In this case, "throw" refers to the offset of the pivot point of the caster. With most casters, the fork must rotate up to 180° when the unit reverses direction. With a zero throw, the casters are always oriented in the direction of travel. From Triple Swivel Caster from Rose Brand Also called Triway Swivel (Turtle) Caster by Mutual Hardware.