However, cages keep balls from scuffing directly against each other and so can reduce the drag of a loaded bearing.

• 搭建一套局域网即时通信系统其实并不是一件庞大的工程，一套即时通信的搭建构成可以分为二个部分：即时通信服务器端软件安装和即时通信客户端软件安装。