The contract underlying is the price of a single bitcoin, according to Interactive brokers. Trading for the CBOE futures was launched on Sunday, and the broker's demanded margin for long positions is $9000.
"The introduction of short sales was necessitated by the large premium of the January futures contract over the price at which Bitcoin trades on the physical venues,” said Thomas Peterffy, CEO and chairman of Interactive Brokers.
Interactive Brokers says it has handled "approximately 50% of the volume since trading commenced" three days ago.
A single bitcoin is worth about $16,600 as of 6pm GMT on Wednesday, according to website coinmarketcap.com.