Two roommates bet their careers on soft pretzels. 20 years later, the Philly snack is more popular than ever.

The hundreds of pretzels in any given Philly Pretzel Factory store look identical, but every pretzel master leaves his or her mark. The angle of the twist, the precise tie of the knot in the center, the curves that form as they are lined up in a row — those signatures are baked in like salty fingerprints.

So say Dan DiZio and Len Lehman, founders of Philly Pretzel Factory. Twenty years after the two began the company in a warehouse in the Northeast, it has expanded to more than 150 stores in 17 states. The onetime college roommates still relish the small joys of the product, and the individual attention paid to each chunk of flour and yeast on its way to becoming a pretzel.

"We have thousands of people who twist pretzels at all our stores," DiZio said, speaking from the test kitchen of the company's Bensalem headquarters. Nearby, Lehman twirled ropes of dough between his fingers, demonstrating the deceptively simple process used to make the 125 million pretzels they sell each year. "They would all sincerely believe that they make the best-looking pretzels. Right? Everyone in this room who twists pretzels all think theirs are the best, right?"

The origin story of the company, which this week celebrated its 20th anniversary, is by now well-known; how DiZio, a former stockbroker, and Lehman, an ex-counselor, hatched a plan to produce wholesale numbers of the pretzels beloved by longtime Philly residents who grew up buying them on street corners. The duo started out sleeping on bags of flour and twisting dough by hand, sweating out long nights over a rickety pretzel machine that had drained their savings accounts.

"Dan likes to talk about the good old days, but it was horrible," Lehman said. "Our friends were all going down the Shore, having fun. We'd be twisting for six hours with no air-conditioning."

In Philadelphia, finding customers was never a problem. People lined up from day one, and within a decade, the company had 10 locations and its first franchise stores. The company grew past Pennsylvania, with several out-of-state franchises opened by former Philly residents. Last year, the company announced plans for 25 stores in Manhattan, the first of which opened last week.

In other states, consumers don't naturally know or understand where or when to eat soft pretzels, said Veronica McKee, vice president of marketing. But with a little education, the pretzels have caught on in new markets.

"They don't know a pretzel is more than Oktoberfest, or something you walk around a mall with," she said. "It's up to us to show how to use them, that they can be great at children's birthdays, after soccer practice, for the office, at holiday parties."

The test kitchen opened last year at the company's Bensalem headquarters, which is, appropriately enough, the former site of the headquarters of Rita's Water Ice. Built to replicate a full store with menus and display cases, it's used to train every employee, even corporate staff, in everything from twisting pretzels to mopping floors. With a little practice, most bakers can twist an average of 1,000 pretzels an hour, DiZio said.

With so much snack-food competition, DiZio and Lehman believe the soft pretzel has endured because it's versatile, delicious, and uniquely Philadelphia. They've heard people tell of parents giving their toddlers soft pretzels to suck on, of refusing to celebrate an Eagles victory without them. On summer weekends, DiZio's father used to buy a bag for their drive down to the Shore.

Even the pretzel makers haven't lost their taste for the product. At a recent company holiday party, the platters of pretzels somehow got picked clean even amid catered trays of hoagies, chicken, and offerings from other restaurants.

“I crave ‘em when I’m on vacation,” DiZio said.