LF-520 ZZ High Quality Flanged Ball Bearing, this is a popular size that could be used in many application that uses this size 2mm x 5mm x 2.3mm. LF-520 ZZ is made of Chrome Steel and can rotate up to 80,000 rpm, each bearing has 2 Metal Shield to protect the bearing from dust or any possible contamination, LF-520 ZZ are pre-lubricated with grease.