Lightweight and more durable! Hsu 2 Fusion: Emerica introduces stiFusion on the new Hsu 2 Fusion Skate shoes. STI Fusion technology revolutionizes the way vulcanized skateboard shoes are made. Traditional vulc shoes are constructed using a centuries old method that combines 3 main parts. First, a piece of outsole rubber is glued to a foam midsole to create the bottom. Next, the upper is glued to the bottom and a piece of foxing tape is wrapped around the 3 parts to hold them together. The twisting and shear forces of skating push these bonds to the limit and occasionally they fail causing the shoe to separate and fall apart.