This is a knee support purchased from an orthopedic clinic for approximately 20,000 yen. It's for one leg only. Size: L It comes with instructions, so anyone can use it. It has two metal supports, which reduces the strain on the knee. It seems it didn't fit, as I only used it once. There is some dirt on the Velcro. Both legs The frame can be attached to either leg. Please understand that this is a used item before purchasing.