(US) Reminder for US markets: today, on Dec 16th, about $4T worth in options tied to stocks, stock index futures and ETFs set to expire in quadruple witching (largest in two years)

- Primary expiry is at US Wall Street open at 09:30ET (14:30GMT)

**Note: The term "quadruple witching" denotes days when a host of equity-linked options and futures contracts expire. It only happens four times a year, once every quarter.