Reliable ProductThis is the U groove wheel pulley bearing made of high quality metal material, with the property of wearable, durable and long lasting, allowing you to do the job without worry. Good PerformanceWith high precision, smooth, low noise, keep a quiet environment used for 3D printer Inexpensive ReplacementTotal 10pcs in one package, Economical replacement to save money, Great 3D printer spare parts extruder accessory to replace your broken one Basic ParametersWith 4mm inner diameter and 4mm thickness, 13mm outer diameter, 1mm groove depth, 2.1mm groove width, please order it according to your needs 100% Money Back Guarantee saleIf you have any questions about the products, please contact us in time. We have 24-hour professional customer service to answer all your questions. We will help you solve it and support all refunds if there is any defect Specifications: Color: Silver Material: Metal Inner Diameter: 4mm Thickness: 4mm Outer Diameter: 13mm Groove Depth: 1mm Groove Width: 2.1mm Package Weight: Approx. 30g Quantity: 10Pcs Package List: 10 x U Groove Wheel Pulley Bearing Delivery Quantity: 10Pcs Product Color: Silver Product Size: 4 * 13 * 4mm Note: Manual measurement, please allow 1 - 3cm error!!!Yeuri