A short butterfly is a long volatility trade. A long butterfly is a short volatility trade. Correct? So whether a butterfly is long or short depends on position of the 2x Calls (or Puts) at X2.
a long butterfly is an active bet that there is is low volatility and price stays around the middle strike price.
Compose of long call, short 2 x call, long call (in increasing strike price)
a short butterfly is an active bet in the opposite direction. You expect high volatility and prices move away from middle strike price.
Compose of short call, long 2 x call, short call (in increasing strike price)
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