Wire pulley groove. Wide application. Especially suitable for iZipline Zip Line Trolley Material:High quality stainless steel. Easy Installation & Replacement Less Friction & Durable Dimension:(Inside diameter)7mm x (outer diameter)30mm x (thickness)9mm. V groove deepness: 5mm 1-YEAR LIMITED WARRANTY, If for any reason you are not 100% satisfied with this Bearings, you can always return it with a full refund in 30 days! Please don't hesitate to contact us First if ever a problem should arise,we'll do our best to help solve it!