Booster - tuning
A booster is used to boost rubbers (tuning); it is applied to the bottom of the rubber, sponge. This product adds tension to the sponge, softening it and making it more flexible, which boosts the speed and spin of the rubber.
The booster provides a very stable long-term performance that lasts 8 to 12 weeks.
ITTF guidelines issued on April 2, 2007 regarding the use of this product
"The rubber must be used without any physical, chemical or other treatment."
As reported by the ITTF, the rubber should be used as it was approved. The ITTF does not approve rubbers as such, it approves "Topsheets". Manufacturers can then select a type of sponge that can be hard or soft, thin or thick, boosted or not! In addition to this, each player can change the sponge and use a sponge according to their own choice (this is very common in Asia).
Boosters are a 100% legitimate technique: this technique does not affect the approved outer rubber, as it only slightly "elevates" the sponge. The rubber does not exceed the total allowed rubber height of 4 mm with a booster.