Humour is one thing, and should not be confused with plain jackass replies. Jalvin's asking a very decent question and none of you even bothered to give him anything that wasn't a childish answer. People who know me know i have a sense of humour.
But let's remember: This forum's ultimate aim is still as a place bowlers can come to for resource. All this "harmless humour" will only make a mockery of our forum and project an image nothing short of rubbish about bowlers. If you wish to engage in kid-talk, there are other forums there; or at least answer the poor chap first.

Jalvin
The SST4 has only interchangeable soles on its sliding shoe.
The SST5 has interchangeable soles
and heels.
The SST6 is the same as the SST 5, but has a wider, broader base for more stability.
For the none sliding shoe, the SST4s and earlier SST5s have only a small rubber patch at the toes for grip, while the later versions up till hte SST6s have almost half the sole covered in rubber.