BCB International sells underwear made to protect your genitals and femoral arteries from injury by explosive blasts. They're made with a double layer of Kevlar and are fire resistant. The shorts have been tested on dummies with substantial success.
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But seriously, after a major bomb blast, could your main concern be the (albeit remote) possibility that all that remained were your dismembered butt and genitals, stored safely in a wacky pair of kevlar underpants (?)...