Pro: Position directly in front of mast base plate on your board to deflect the mast away from the nose of the board if the rig is dropped.
This product is a take on the Jez's Knob idea & works just the same. Ideal for new windsurfers who are still uphauling.
Con: The position in front of the mast track can make maneuvering the board & rig for a waterstart a bit harder if you want to pass the rig over the nose.