WSA are soft and wear out fast where the belt overlaps so I use take off cs22's for cold weather soft tires (decent wear by the way). WSB are warm weather tires (comparable to take off cs27 or 32) and so have longer durability and are actually very durable compared to yoke139g's. After 4 runs I still see the mold lines down the middle of the tire and I knew people were using year old WSB at the nats. WSB are the tires I believe Simo used to win the Finnish nats and are still available from Take Off.