FITS MATCHBOX no. 's 18E,39/40C,49B,50/51B,72A. MOUNTING INSTRUCTIONS:THESE ARE MADE TO THE EXACT MATCHBOX SPECS. HOWEVER, THE ORIGINAL TIRES WERE MACHINE MOUNTED UNDER PRESSURE WHILE STILL WARM. THE TIRES AS WELL AS THE PLASTIC HUBS COULD EXPAND OR CONTRACT AFTER COOLING.