Distribution of Boston Beer Co.’s Truly Hard Seltzer, not its flagship Sam Adams offerings that it’s known for, have even further runway as a bevy of flavors helped send shares to record highs this month, according to Macquarie analysts.

IRI market research all-channel data show second-quarter shipment growth for the Sam Adams brewer of 21 percent, almost double Macquarie’s expectations, despite not properly capturing the potential sales boom for Truly seltzer, analyst Caroline Levy writes. “It is hard to know just how high shipments will actually be” for the beverage, given Boston Beer over-shipped the seltzer to “ensure adequate distributor inventories for the summer selling season.”

Investor optimism on the growing sales potential for Truly, paired with Boston Beer’s plans to buy Dogfish Head Brewery in a $300 million deal, vaulted shares to a record high earlier this month. The brewer is up more than 60 percent year-to-date — 10 times the 6-percent advance for the S&P 400 Consumer Staples Index. Shares swung between a 2-percent gain and 1-percent loss after the market open Monday, as the stock traded as high as $395.48.

Second-quarter sales of the bubbly drink that’s taken beach and pool parties by storm grew by 163 percent while sales of its Twisted Tea grew 22 percent, Levy wrote, citing IRI data, which helped cover a soft launch of the company’s Angry Orchard Rose and declining sales of beer.

Sales of Truly and Sam Adams’ non-beer drinks account for more than three-quarters of sales, Levy noted, with further growth likely for Truly if it can follow the trajectory set by other beverages, including Twisted Tea and Diageo Plc’s Smirnoff Ice. The spiked seltzer industry also fits nicely as gluten-fee offering, with Angry Orchard Cider having the potential to be a “cash cow” for the company, Levy continued.