moon and sun in all black ring Details Flip Rings are medical grade silicone, hypo-allergenic, ultra-comfortable, waterproof and won't rub off on your skin or clothes. Weight: Incredibly light Width: 6mm Thickness: 2mm Size Flip Rings are one size. They are designed to fit snug but will stretch and conform to your finger. Technically speaking they are a size 7 (17.2mm diameter) which is the average women's ring size in the U.S. Not sure what your ring size is - it doesn't matter. Wear them on any finger, thumb or even toes. It's all good.