Deep groove ball bearings have many series as follows:1600 series,6000 series,6200 series,6300 series,6800 series ,6900 series and each serial has several types such as :open, zz，2rs and each type has many different sizes. The retainer of it is normally made from low carbon steel 08F,if required ,it also made from nylon ,fiber reinforced phenolic resin ,plastics or other stocks