go on to mrtyre.com, they explain what the letters mean, i am sure it is the speed rating of the tyre. w's can cope with faster speeds. obviously later galaxy's have a higher top speed than the earlier ones so ford will have uprated the speed rating of the tyre. if you oly potter around town the lower h ones should be fine but if you race against jenson button at the weekends then i would stick with the higher rated ones.