The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 4,253.30 crore in the futures & option segment on Monday.According to data released by the NSE, FIIs were net buyers of index futures to the tune of Rs 4,063.52 crore while sold index options worth Rs 162.42 crore. They were net buyers of stock futures to the tune of Rs 367.16 crore while sold stock options worth Rs 14.96 crore.