Open interest in HSBC (HBC, news, chart, volatility) March 45 puts increased by more than 85,000 contracts. Some appears to be due to straight put buying. For example, in the final hour of trading, a customer bought 5,000 for $4.60 a contract. The bulk of the open interest was due to a customer purchase of 75,000 that traded along with the purchase of 650,000 shares at $47, 12,500 March 35 puts at $1.35, 12,500 March 40 puts for $2.45, and the sale of 50,000 March 50 puts for $4.30.