Short Pimples Rubber
The pimples are facing out and are part of the playing surface. They are generally very fast but the ability to impart spin is less than Pimple In rubbers. Short pimple rubbers are used by speed players that play a fast attacking game close to the table.
Thickness of Sponge
The thickness of the sponge will affect how fast the overall rubber will be, and also how much control it has. Thicker sponge is faster but has less control than thinner sponge. Most attackers use sponge of either 2.0mm or Max thickness (2.2mm), while many defenders use thinner sponge for the extra control. Most professionals use thicker sponge for increased speed.
It is possible to not use sponge at all with pimple out rubbers. This is classified as OX, using no sponge can be an effective tactic for those players who defend or twiddle their bats!