The Ergo-X2 Caster Series is a premium highly engineered caster designed to reduce the force needed to push or pull carts. The patented swivel caster design features two precision machined offsetting ball races in a compact assembly to minimize one of the final unresolved issues with swivel casters: lock up. A typical swivel assembly in a caster has only one pivot point. The Ergo-X2 Caster essentially provides a second pivot point that reduces the startup force to get the cart moving when lock up is present. Hamilton’s Ergo-X2 reduces these binding forces by providing internal relief via the offset swivel raceways. So the Ergo-X2 paired with one of Hamilton’s low start up poly treads is the safer way forward. US Patent No. 9,051,965