Custom height,width and firmness based on the riders size and type of riding. They vary quite a bit from seat to seat and I've seen a few odd balls in the flea market get sold multiple times as they must not have fit the new owners very well. The suede cover really makes the seat work, no sliding and very comfortable. I've had mine for a couple of years and it is worth every $$ and then some.
Born 10,000 years too late
Scientific Wild Ass Guesser:hmmmm