I have used Stiga DragonGrip. It is tacky, hard rubber. It is not fast at all. I used Tibhar K1. It is very tacky, maybe slightly softer than DragonGrip and just as slow. I am hoping that Donic BlueGrip S2 is much faster with a softer rubber sponge.
am using S2 on backhand and K3 on forehand. S2 is softer, slower and more control. K3 is slow in touch game but lot of power and catapult in open game. I found it very good for forehand. But K3 is much harder than S2.