 Sometimes known as "I kill you later" contracts, accumulators typically last for a year or less and terminate early ("knock-out") if the stock price goes above a threshold ("barrier").The basic idea of an accumulator contract is that the buyer speculates a company will trade between a certain price range (the range between the strike and the knock out price) within the contract period, and the issuer bets that stock will fall below the strike price.Note that the buyer holds an obligation to buy the shares at the strike price and not the option to buy.