E-mini S&P
E-Mini S&P, often abbreviated to E-Mini, is an equity index futures contract traded on the Chicago Mercantile Exchange's Globex electronic trading platform. The notional value of one contract is US$50 times the value of the S&P 500 stock index.
It was introduced by the CME in 1998 after the value of the existing S&P contract (then valued at $500 times the index, or over $500,000 at the time) became too large for many small traders. The E-Mini quickly became the most popular equity index futures contract in the world. The original ("big") S&P contract was subsequently split 2:1, bringing it to $250 times the index. Hedge funds often prefer trading the E-Mini over the big S&P since the latter still uses the open-outcry pit trading method, with its inherent delays, versus the all-electronic Globex system.
The contract trades 23.5 hours a day, five days a week, on the March quarterly expiration cycle.