The Fusion 2.0 is a salute to the original Karhu ‘fusion’ model from 1996 when it was the top running shoe in the collection. To bring back the ‘Fusion’ from the archives, Karhu reworked the model with its original designer and launched it as the fusion 2.0. suede upper technical sports mesh rope laces New to the fusion 2.0? Unisex sizing in US men's.