F4 has been developing hydrofoils for windsurf boards over the last year and recently went into production. They also manufacture the RS:Flight carbon foils for Neilpryde, thus a strong simlarity between those brands.
The new windsurf foil is based on carbon prepreg construction and is very stiff and strong. This new hydrofoil is allowing riders a new level of performance and stability enabling upwind and downwind performance comparable with formula windsurf boards.
Flying above the water allows for a consistent speed since the motion through the water is not significantly affected by the waves and chop. The ride is particulary smooth and enjoyable.
Riders can however use much smaller sails than formula boards, in the 5m2 to 7m2 range.
Source and pictures on this page: F4 Fins