16mm hinged donut bails fit most 30-40mm round gemstone donuts. With the hinge, they are easy to use and even trade out donut colors! They fit donuts up to 6mm thick, which means they will fit most gemstone donuts, but not all.
26mm hinged donut bails fit most 50mm round gemstone donuts. Easy to use and trade out donut colors! They fit donuts up to 7mm thick, which means they will fit most gemstone donuts, but not all.
Donut bails for Swarovski #4439 crystals give you an easy way to turn square crystal rings into a pendant, rather like a setting for a crystal stone (they are not designed to be taken on and off). Some styles have a loop so you can dangle a charm inside, and some are classic and smooth, with no extra loops.
Gemstone donuts and other handmade or natural material donuts and pendants vary in diameter from item to item and batch to batch.