About this product: R1660ZZ (Inner diameter = 6mm, Outer diameter = 16mm, Thickness = 5mm) Sealed on both sides with shields to retain lubricant. Made of chrome steel (GCr15). Durable and resistant to deformation under high loads, with excellent wear resistance. ABEC 1 (P0) tolerance, most commonly used Z2 noise level. Pre-lubricated, easy to maintain.