When a country converts to metric it does not simply change the dimensions from inches to millimetres, but takes the chance to make the range offered more rational in both terms of international usage and what already exists. So some things change a lot, while others do not change much.
Tubing has remained in inch sizes, but it is described in metrics. Tubing is specified by its outside diameter (OD) and wall thickness. The main sizes used for the legs of trolleys to which castors are fitted are shown in this table below.
Note: When fitting wheels to axles you need to be careful as to whether the axles are made from wire, black bar or bright round—as this might affect the actual size and thus the neatness of fit.
You will also need to be careful if the article has been powder-coated as this could add to the diameter and make a fit too tight. In many wheels we can offer special "off-standard" bushings at little extra cost.
Check your needs carefully, then talk to a Fallshaw representative.