The Foreign Institutional Investors (FIIs) were net sellers to the tune of Rs 662.82 crore in the futures & options segment on Monday.According to data released by the NSE, FIIs were net buyers of index futures to the tune of Rs 178.26 crore and bought index options worth Rs 475.18 crore. They were net buyers of stock futures to the tune of Rs 5.34 crore and bought stock options worth Rs 4.04 crore.