The Child Crank Option is made to be used with children between 5-10 years old who are unable to reach the pedals with the rear saddle fully lowered. The installation instructions are included in the box. When installing this kit on a tandem, make sure that its rear seat tube is 1 1/4" or 1 1/8" in diameter and it is equipped with crossover drive (chain on left side of bicycle connecting captain to stoker crank). In order to use the 39 tooth chainring that is supplied, the rear crossover arm must have the 130 mm bolt circle with five arms, If you need to adjust the reach of the handlebars, you can flip the handlebars 180 degrees so they face back. An optional adjustable stoker stem may be available.