The answer is synthetic fiber. Mass-produced, ready-to-wear wigs are built from synthetic fiber to keep the price down.
Wool, angora, and yak hair do show up in wig-making, but on the theatrical and fashion side, where pieces get blended with human hair for a specific look. Off-the-rack wigs built for everyday, no-fuss wear skip the custom blending and go with synthetic fiber by default.
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