This model has 12.7 mm (1/2″) bushing. Polyurethane Beach Balloon Wheels are specifically designed to navigate challenging terrains like soft sand, mud, gravel, grass and rock. They are also great on hard surface terrains like streets and sidewalks. Moving heavy, awkward loads is easy with our wheels, Dimension: 30 x 18 cm (11.8 x 7″) Width at bushing/bearing: 18.5 cm (7.3″) Maximum Payload: 55 kg (121 lbs) Weight: 1.32 kg (2.91 lbs) Tire: Polyurethane Hub: Polypropylene Ideal pressure: 2.5 psi (0.17 bar) Pressure range: Low Pressure 2-4 psi (0.14-0.28 bar) Temperature Range: -15 to 75 c (5 to 167 F)