Starboard is the market leader for windsurf hydrofoils with 25% market shares. It’s quite surprising to see Slingshot at a solid second place with 17% market shares. Note: Windsurf Market Share Chart
Knowing that Slingshot is mostly known as a kitesurf brand (even if they used to be involved in windsurfing years ago) and that they only focus on the freeride side of windfoiling.
Third place is for Neilpryde (or F4) foils with 11% market shares. Those three brands are selling more than half of the windsurfing hydrofoils currently on the market. Note that some brands have a local competitive edge: Slingshot is by far market leader in the US, AFS and Zeeko are the most popular brands in France, but Lokefoil and Taaroa are well established as well.