Originally Posted By: Andy
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I spent a couple of days this week giving out the mini Fox-40's to AF guys in the SAR and air crew survial business. I heard from several that the pea-less designs do have the advantage in working in extreme cold environments. ...
Andy

Well yeah, the darn pea in the pea whistles used to freeze up and then they would be hard to get any sound out of at all.
The metal ones would freeze to your lip too if you were not careful.
I remember carrying the metal pea whistles in my inside parka pockets so they would stay warm enough to work and not tear pieces of my lip off.
The plastic Fox whistles were a huge improvement.
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May set off to explore without any sense of direction or how to return.