Sponge thickness for learning topspin

Hello coach, I suppose that the sponge is very important to do and to learn topspin, my question what thickness, 2 mm or less the sponge hard or not hard?

Hi Martinand,

I think when learning the topspin go for something between 1.5 to 2mm depending on the speed of the rubber as well.  So for a faster rubber go for 1.5mm and for a slower rubber you can venture out to the 2mm.  Try the softer sponge as well as this will give you a better feel for the topspin initially.