Carbon belt drives are all the rage. They are clean, light, and nearly indestructible. However they provide limited options. Rear cogs smaller than 22T is unavailable for Shimano Alfine hubs. Additionally only select chairing are available 50, 55, 60, 66, and 70. This means you need super large rings for a small wheel folding bike. Standard chainrings come in every tooth option, and the same is true for rear cogs ( so you can go small upfront and small in the rear ). There are limits to gear selection, however it has improved over the last few years. Hopefully Gates will introduce more options in the coming years.