The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 565.56 crore in the futures & option segment on Tuesday.According to data released by the NSE, FIIs were net buyers of index futures to the tune of Rs 343.79 crore and bought index options worth Rs 11.42 crore. They were net buyers of stock futures to the tune of Rs 211.20 crore while sold stock options worth Rs 0.85 crore.As per data available on the Sebi website - FIIs were net sellers of stocks worth Rs 250 crore in the cash market on Monday. Mutual funds net buyers of shares worth Rs 33.07 crore on the same day.