Bung (for swiss ball) (Q40461)

A spare bung for my swiss ball (a fitness-mad 75cm one). I decided to print 2 x bung.stl as that way possible de-lamination doesn't mean having rubbish inside the ball. My printed one appears to work, i.e. it is airtight. bung.stl works fine, even though it doesn't appear to render on thingiverse.