S688ZZ ABEC-5 Shielded Ball Bearings Stainless Steel Miniature with Ceramic Balls Pack of 10 Bearings Pack of 10 Stainless Steel Metal Shielded Ball Bearings and ceramic balls ABEC-5 quality, these are a popular size that could be used in many application that uses this size 8mm x 16mm x 5mm. Bearings are made of Stainless Steel, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease.