SQQQ

ProShares UltraPro Short QQQ (SQQQ) is an exchange-traded fund designed to move in the opposite direction of the Nasdaq-100 index at three times the daily magnitude. When the Nasdaq-100 falls 1%, SQQQ is built to rise roughly 3%, and vice versa. It does not represent ownership in any company; instead it uses financial contracts called swaps to deliver that inverse exposure. Traders use it to profit from, or protect against, tech-stock declines.