Cannondale lefty fork. From my understanding, single strut landing gear are used to minimize the space/area required for the landing gear bay because the more compact the landing gear is, the less depth is required to stow it. Instead, it has now become a proprietary system by Cannondale that receives limited aftermarket support, and is butt ugly as well. The landing gear tubing (fork) is stouter then conventional designs because it needs to be, in order to resist flex.