BY midafternoon on a recent Saturday, Bierkraft, the beer emporium and grocery on Fifth Avenue in Park Slope, Brooklyn, was half-filled with customers, many of them parents with babies or toddlers in tow. They were browsing the more than 1,000 varieties of bottled beer or surveying the listing of selections available on the 13 taps and 3 cask lines. Some carried a good-sized satchel.

Diaper bag? Gym clothes?

No. It was a tote for their growlers.

Growlers  64-ounce glass vessels that look like a moonshine jug  have become the beer accessory of the moment. And the jugs, filled at taps in bars and stores, are not just the toys of the bearded, flannel-shirt, beer-geek set.

“In the beginning we tried to figure out, ‘Who’s going to be our market?’ ” said Ben Granger, 32, an owner of Bierkraft, which began filling growlers in spring 2006. “We thought, mullet-heads and beer-bellied dudes. But the first run was ladies with strollers. They will tell you they’re buying them for their husbands. Three weeks later, they’ve got two. One’s his and one’s hers. The next one that caught me by surprise was dads coming in with their kids. Then there’s the beer crowd who’ll rush in to get on this or that before it’s gone. There’s no age limit.”

Michael Endelman, a journalist at Rolling Stone, is one of those growler-loving fathers. “I don’t go to bars too much anymore,” he said, gesturing to his baby daughter Mimi. “It just seems like a great way to be a beer geek without going out.”