The HZ72 P36 grit zirconia belts are supplied on a strong polyester backing which means they can be used wet and dry. The polyester backed cloth also improves the grinding pressure and the speed of stock removal.
The FX87 P36 ceramic belts will give you all the benefits of the HZ72 plus a faster cut rate, a cooler cut (from the grinding aids in the belt coating) and a longer life (from the high performance ceramic abrasive grain)