Based on Wookieepedia the V-4X-D ski speeder, also known as the Resistance ski speeder, or the Single Pilot Operator, was a high-powered assault vehicle manufactured by Roche Machines.
The V-4XD ski speeder was a low-altitude airspeeder used by the Rebel Alliance during the Galactic Civil War. The ski speeder used a stabilizer strut to keep balance when moving across alien terrain. The strut could be retracted so that the speeder could gain some altitude, but this would often make the craft experience severe wobbling.