These Turbo Eight handcuffs are loosely based on a design invented by either a US army or navy man called Lilly or Lillie, no-one has decided which one for sure,  The story goes that the inventor ended up restrained by his own design as he was violently mentally ill (see picture of the original).  These very solid copies, weighing just less than 700 grams or 1 1/2 pounds, are very secure and difficult to pick so be careful with the keys. The internal circumference is about 18cms each side (7 inches)