http://www.anarchymodels.co.uk/
HS are reusable,
HD has limits to how many times you can use it as it is basicly a film.
I havent used them myself, but i have used standard hobby stencils that are reusable and it only works well on flat surfaces, like a
40k rhino or leman russ. They dont work well on say shoulder pads of a
40k imperial knight.
Based on the youtube vids of the
HD stenciles from anarchy, they work pretty good on curved surfaces.