General description These 4Pcs Series 48X50mm Yellow Silver Nylon Steel Flat Roller Bearing Guide Wheels are designed for various applications including electric door top wheels, pan door nylon clamping wheels, iron door wheels, electric door guide wheels, track wheels, and pulleys. Each wheel features two 6201 insert bearings, making them great replacements for old or damaged wheels. Technical specifications Size: 48x50mm Material: Nylon Color: Yellow Bearings: Two 6201 insert bearings per wheel Measurement error: +/- 1-3 cm Other information Package Contents: 4 x Guide Wheels Note: Light reflection and different displays may cause the color of the item to differ slightly from the real thing.