Huck, all the B series have springs but they don't seem to do much. But the 2910 has a seat that travels up and down about 2 to 3 inches, with a variable tension control that you can adjust for your weight. Sometimes it almost feels pneumatic to me. My direct comparison is to the BX (standard B) seat. On the BX I would constantly bounce up and down with my seat banging up and down on the tractor seat if I went fast, with me sometimes lifting slightly off the seat. Going over the same ground at the same speed with the 2910, it is the seat itself that travels up and down. Occasionally, it will bottom out, which I could probably fix with the tensioner.
Again, it is a big difference. I'm sure there are aftermarket seats from sources such as Bird has posted. Chalkley has one about which he sings rhapsodies.
Glenn