well, it's called a "wide base" wheel, not a "super single"
super single's are normally used in mining applications, and on cement mixer trucks, etc... they have a fairly standard profile, like 18R22.5
a wide base, will be a low profile tire, something along the lines of 375/50R22.5
They've been popular in Europe for about a decade, and are starting to catch on here; they're supposed to have less drag than a comparable dual-tire application, therefore enhancing fuel economy... most industry insiders are saying that when they really catch on, you'll be able to reduce your capital outlay for a complete set of tires by about a third over a conventional dual-wheel set up... I guess time will tell, as I've not seen them on more than a handfull of tractors and trailers... I know Buske Transport is converting their fleet over to them...