Our office has bulk swissballs... very cheap (NZ$30??). Boss is getting new carpets and has dictated that we all use them (to reduce wear on the carpets). I've used one for about a year. They are great, my back pain of +5yrs has gone (well...I went to chiropractor too...but anyway...). And when customers come by you can all look really stupid together! When people get excited they bounce up and down, also very funny.