There are different types of balaclavas.
There are the ones that Stinky Nut Rappa was talking about which cover the head and ears but not the face:
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/ __ \
|( ) | <-- Sort of vaugely like this
| | | |
And the ones that Coldfire is talking about:
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| 0 0 | <-- I think perhaps like this?
| 0 |
There are lots of different types of balaclava, although I have heard the one directly above called a ski-mask (even though I've never seen skiers wearing them, just terroists and criminals)