You need to have this replacements to survive at any performance if your Kazoo Spare Diaphragm suffers any damage by pushing it accidentally with your finger (or someone's else - as it is a "curios and exotic" instrument for those who don?t know it and they will touch it for sure...) or if damaged by carrying it in your pocket or bag without an case for it. Easy to change: unscrew the ring, replace diaphragm, screw the ring, play and have fun! Simple as that.
Ordered Gewa Kazoo here, and sure thing I ordered spare diaphragm. Sure thing you won't have to change diaphargm often, but having a spare one is good way to get no worries about breaking your little fun.
To change your diaphragm simply unscrew the ring, swap the diaphragms and screw the ring back.