They are 4 wheeled downhill bikes. They are designed for people who can no longer ride due to paralysation of their lower bodies. There are a bunch of guys who shred at the Forest of Dean. It's such a cool idea, however the design has flaws such as, parts that rub on the knees and create big wounds and because the guys that ride these have no feeling in their legs, they don't realise until they finish. They are redesigning to make them lighter, more agile and more comfortable. It takes a lot of bravery to get back on a bike when you have a life changing crash, and these aren't the easiest things to ride in sure! Top props to these guys. They are unsung heroes of the sport!