30mm round with 8mm central opening. This piece is highly polished. Each donut is unique in colors as they are totally natural. some have more pink than others. Some have a little beige in them as well. All are naturally beautiful and have been hand picked for their quality in color variations. Many of you have heard that conch is an aphrodisiac. We just think it is beautiful. You never know who you may attract when wearing this beautiful shell? We had a larger 40mm version that sold out last year & know you will enjoy this size as well.