The Bank Nifty index has been outperforming the benchmark Nifty. It has gained 4 per cent in the past one month and 16 per cent year-to-date (YTD). In comparison, the Nifty is up less than 2 per cent both on a one-month and YTD basis. Technical analysts say investors use the weakness in the banking stocks as a buying opportunity. “The index remains in a buy-on-dip mode with strong support at the 40,500-40,000 zone where aggressive put writing has been witnessed. The index once breaches above 41,500 will witness an extension of the up move towards 42,000 where the highest open interest is built up on the call side," said Kunal Shah, Senior Technical & Derivative Analyst at LKP Securities. The Bank Nifty index last closed at 41,123.