I ordered several float balls for a sight glass, as an experiment. The balls are a bit smaller than my glass cylinder, but they still work. This is for my Big Berkey water filter. Berkey sight glasses don't come with float balls, so you have to get close to them to read the level. Now that the bright red ball is in place, you can easily see how much water is left from across the room, and it reflects off the SS container, as well. Espresso parts was the only place where I could find one that is intended for use in potable liquid, and their shipping costs are reasonable. My order arrived quickly, and it was correct. If I need any more of them, I know where to go.