I use these with all my hi hat clutches, I bought my first set before almost 2 years and they didn't change shape a bit, which I cannot say for regular hi hat felts that came with my stand.
The only con is that some hi hat clutches have limited amount of space for upper felt so top hat can be little stiff. I solved this problem by using combination: upper felt is regular type, and the lower one is Cympad Optimizer.