The problem that we ran into with them was that the 'falling rate' of the spring design was wrong. You could say they were built backwards. The spring was strong when the seat was at the top, and got weaker as the seat moved downward. So, if a bump was hard and the seat post began to drop, the rider would end up all the way at the bottom of the action. Then they would have to lift their weight back off of the seat to get the seat back up because the spring was too weak to actually lift the rider.