How high are the highest wearable high heels?

For experienced high heel wearers it is generally agreed that the highest heel that can be worn comfortably is between 5 and 5 ½ inches. This is assuming there is no platform sole and the heel is a stiletto, a high heel shoe with no platform sole is often referred to as "single sole". It should also be remembered that heel height for a particular shoe is approximate and is dependent on shoe size, for example a 5 inch heel will increase in height to 5 ½ usually if the shoe size is greater than E.U. size 41. This is to maintain proportion between length of the shoe and height of the heel.