These have an unstretched o/d of 12.6mm, i/d 11.4mm and are 2mm wide. They suit many Hornby small wheel tender drive and diesels. Examples include early versions of Class 25, 29, 35, 37, 42, 43, 47, 52, 58, 86, 87,91, early 101, 110, 142, Brittannia, King, 9F, Duchess, Black 5 and more. For 9F check the relevant service sheet. They fit Hornby number R2057 and lower.
If you are unsure, message me with either the R**** number or running number or both.
They do not fit Railroad Plus Class 47. For those use Lima large ring style tyres. The Class 91 with the 5 pole motor uses X8865.