If you are in S. California, give me a call(626 794 6789). I might have a used one for sale. It was on my '84 triplet, 125 mm cranks. My son and daughter both used it. By the time my son was 6 or 8, I think he was mostly switched to riding a Tandem Tuesday with crank shorteners. He is 17 now and uses 175 mm cranks. You do take the child conversion off when they are big enough. They are easy enough to take off, that converting it back and forth is not too hard, if you want to ride with another adult.