6x17x6 Metal Halo bearing 606ZZDimensionsMETRIC: 6mm (Inner) x 17mm (Outer) x 6mm (Width)STANDARD: 0.23622" (Inner) x 0.66929" (Outer) x 0.23622" (Width)Fits:Tra3661 Velineon 1600XL 6s for XmaxxTra3491 Velineon 1200XL 8s for Xmaxx