I've just used Spartite.
The 2 principal reasons for doing so was that gap between the mast and mast ring was too narrow for wedges and the gap had no taper at all. Spartite or something similar seemed the best option.
There is a good U Tube video on using Spartite and our Spartite kit came with good instructions. Because our gap was so narrow we pushed the foam up from underneath to form the dam. It all worked very well, using the smallest Spartite kit costing NZ$170 delivered. No sailing yet.
Rob