8Pcs U-Groove Nylon Guide Pulley Rolling Bearing H-Groove Wheel 5x21x7mm for Driving Machinery Doors and Windows

一、Product Description8PCS Green U-groove POM Bearing Rollers. Constructed with wear-resistant green POM outer shell and built-in precision ball bearings. Features smooth, quiet rolling, low friction and anti-rust performance. The U-shaped groove perfectly fits guide rails, cables or sliding tracks, preventing derailment effectively. Ideal for sliding doors, windows, furniture slides, machinery guides and DIY transport assemblies. Compact size, easy installation, stable load capacity, long service life. Great replacement rollers to upgrade sliding systems for smoother movement.二、Detailed Correct Usage InstructionsCheck the pulleyInspect each roller for cracks, bearing jamming or surface defects before installation. Confirm the axle hole size matches your mounting shaft.Mounting operationSlide the shaft through the pulley’s central bearing hole. Secure with fasteners to avoid axial wobble; do not over-tighten to reserve free rotation space.Align the trackPlace the U-groove onto the matched guide rail/cable. Ensure the roller stays vertically aligned with the track to avoid unilateral abrasion.Test sliding performanceManually push the sliding component back and forth. Verify rollers rotate flexibly without stuck, abnormal noise or derailment.Load & maintenance noticeDo not exceed the rated load. Keep grooves and bearings free of dust, grit. Clean regularly; avoid long-term exposure to corrosive liquid.Quantity arrangementDistribute the 8 pulleys evenly on both sides of the sliding part for balanced force, preventing tilt and uneven wear.