Here's what other sites are saying:
The Skull Cap from Black Diamond is a fitted alpine/winter insulation beanie for under your helmet.
Black Diamond's Skull Cap understands that a climbing helmet alone often is not enough to keep your head warm when alpine or winter climbing. The Skull Cap provides that essential extra barrier against the elements, without the bunching up of standard headwear beneath your helmet.
- Mountain Gear
Black Diamond Skullcap (Fall 2010) FEATURES of the Skullcap by Black Diamond Lycra top retains heat Breathable fleece coverage of forehead and ears Ergonomic pattern designed to fit underneath a helmet ALL CLIMBING SALES ARE FINAL.
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