There have been many makes and types of 2" 'Bolt-under' kingpin (the type that bolts up into a backplate/retention plate, which is welded to the trailer rubbing plate). Some are interchangeable and some are definitely not interchangeable - it is therefore very important to identify the correct replacement kingpin.

First establish the make and part number, marked on the kingpin and use a cross reference list to identify the correct Capus replacement part number. If there are no marks or they are illegible, then measure the critical dimensions and check the type of fixing bolts, against the chart below.

Some backplates are stamped with the part number or a colour code which indicates the thickness of trailer rubbing plate it is designed to be welded to, this is not the depth of machining (see below)