They are bullet shaped foam with a hole in the middle and wings. Peanuts are also used, same idea no wings. Look through some ot the past posts, lots of info and pics.
I just found out that the Rochester area meeting will be at RIT on Monday March 14th at 7:00 PM in the Carlson Auditorium, in the Imaging Science Bldg. There will be a press release coming out soon.