The dental dam which is displayed in the exhibition came in a pack of five, so hopefully the rest of them are still around. You'll recognise the box by the fact it has the creepiest disembodied smiling mouth on it, it looks like a clown mouth. You may also be able to smell them; they smell strongly minty. There is a decent chance that we threw them out, though, because the box was giving us the fear. If the dental dams haven't been chucked out, they'll be in one of the plastic boxes opposite the green sofa, probably either the one marked "contraceptives", or the one marked "horrible vagina stuff".
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