He notes: the shown hoop has a diameter of 78 cm (~31 inch). The moat's diameter (measured from the center of the moat's trough) must have the same diameter as the hoop. This size hoop is good for putting one person in a bubble. An 85 or 90 cm should make it easier to put more than one person into a bubble! Thomas wrote: "When using the KIB moat one soon gets a lot of foam. For me the easiest "remedy" is a short break, cleaning the hoop with a towel and burn the foam in the moat - something I wouldn't advice to those using an inflatable pool as a moat ;)"