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Having problems with our terms and abbreviations/acronyms? Search our list of glossary terms below.


Centre Bore CB

The Centre Bore (CB) is the diameter of the hub spigot/locating hole in the back of the wheel. Measurement is taken by measuring the spigot or the hole from edge to edge in mm. For example, a 57.1CB means the diameter of the hub spigot is 57.1mm.



Chromium plate as a protective finish, used to prevent rust.


CNC Machine/Machined

CNC Machine/Machined is the process of manufacturing a part by an automated, pre-programmed machine that uses written codes to perform every movement.



A collar reduces the size of the wheel bolt hole. This is typical when using a bolt in a Range Rover or Land Rover wheel.


Computer Numerical Control CNC

Computer numerical control (CNC) is a method for automating control of machine tools through the use of software embedded in a microcomputer attached to the tool. It is commonly used in manufacturing for machining metal and plastic parts.