A griptop surface (sometimes called rough top) conveyor belt is a raised rough pattern that greatly increases the friction of the belt surface, reducing product slippage.
A griptop is particularly useful for solid objects such as packages etc when going up or down inclines.
Note, however, that it also increases the thickness of the belt, which may require larger diameter drive and tension rollers.
It is normally associated with PVC belting, though it is possible to get rubber grip-top. It is NOT normally available in PU, as PU belts are normally required to be easily cleaned, and the grip-top would defeat this.