The rest of the kit is of a great convenience as well. Write in Rain paper, nylon cord, nylon line and fresnel lense all which he does not have conveniently packaged and wrapped.
The whistle I found bulky and didn't work that well and about the same space volume of a cut down fox 40 anyway.
It was worth the purchase for the mirror alone as no other designated signal mirror of the same weight fits in an altoids tin.
Flip