This Rocker is a universal attachment to turn almost any four legged chair into a real rocking chair. According to the product description, "depending on the chair of your choice, you can get any kind of rocking chair; from a superlazy to a more active rocker." You won't find me with a granny chair, I'll take the "more active rocker" so I can rock out like the best of 'em. Unfortunately, it doesn't look as if the product is for sale yet. This would be a fun attachment for human legs, though; skateboarding is so last season.