Definition: According to Law 188.8.131.52 of the ITTF rules, sandwich rubber is a single layer of cellular rubber (known as the sponge) covered with a single outer layer of ordinary pimpled rubber (known as the topsheet), the thickness of the ordinary pimpled rubber not being more than 2mm.
According to Law 2.4.3 of the ITTF rules, the layer of ordinary pimpled rubber may have the pimples inwards or outwards, and the total thickness of the sponge layer and ordinary pimpled rubber layer (including glue) may not be more than 4mm total.
The sandwich rubber is glued to the blade with the sponge side inwards.
The term sandwich rubber is not in common usage – most players simply say rubber when they mean sandwich rubber.
Also Known As: sponge rubber, rubber