I had zero problems with a HealTech GIpro DS, but it is expensive. I also really didn't need it. At lower speeds, engine sound and rev needle let me know if I was in the right gear. At higher speeds, the only gears I could be in were 4th, 5th and 6th or the noise would be obvious. In 5th on a Wee with stock sprockets, the rev and speed needles are parallel. If the rev needle is past the speed needle, the gearbox is in 4th. If the speed needle is past the rev needle, the gearbox is in 6th.