The ring tape measure works like a belt. Thread the end of the belt through the slot to form a ring. Place the ring tape measure on your finger and pull tight until it is comfortable. It has to go over the fingers and limbs without further ado. Read the ring size when the ring tape measure is comfortable. You can do this several times a day to get an optimal size. If you order a ring from us, we will deduct the price of the ring tape measure from the purchase price.