Crypto traders are snapping cheap, out-of-the-money (OTM) bitcoin calls at levels around the cryptocurrency’s lifetime high of $69,000. Over the weekend, many call options at strikes $65,000, $70,000 and $75,000 changed hands on Deribit, the leading crypto options exchange by volumes and open interest. On Deribit, one options contract represents one BTC. Call options give investors the right to buy the underlying asset at a specific price by a stated date, while puts confer the right to sell. A call buyer is implicitly bullish on the market. The mass buying of higher strike calls reflects a bullish mood among sophisticated market participants. “We see a concentration of open interest in $50k calls and have seen flows in $50K, $60K and $75K calls in the listed options markets from April to June maturities,” Kelly Greer, head of Americas sales at Galaxy, told CoinDesk in an interview.