The difference between banker and bassist? About one and a quarter inches.

That’s the width gap between a classic necktie and the extremely skinny style that harkens back to ’80s rock bands—and the fall 2005 runways, which designers flooded with dental-floss cravats. “The fashion community tried to put it on the trading floor, and it just didn’t happen,” says Tom Kalenderian, chief men’s buyer for Barneys New York.

But the tie that was too extreme for Wall Street did end up leaving its mark—in part because other aspects of a fashionable man’s ensemble were also getting slimmed down. “The trend in clothing is more fitted jackets and more narrow lapels,” Kalenderian says. To avoid having their ties look clown-size against the modern suit silhouette, manufacturers had to take a little off the sides.

“We responded by bringing the tie down to about three and a half inches, and it was very successful,” says Melissa Lawrence, senior vice president for sales at Mulberry Neckwear, which designs and cuts ties for a number of labels, including Ben Sherman and BCBG Max Azria. Mulberry’s ties had previously measured three and three-quarters inches wide, almost across the board. A quarter of an inch might seem like an imperceptible shift, but any more could be disorienting to the mainstream customer.

“People are buying these ties and may not even realize [the change],” Lawrence says. “But the look is more clean, and it’s a way to get that more moderate guy into the modern look.”

Some high-end tie makers had a harder time adjusting. “It’s frustrating for us because when you go down to three and a half, you can’t appreciate the fabric,” says Susan Benson, director of marketing for Robert Talbott.

Luckily, there’s still a place for broader fare. Both Kalenderian and Colby McWilliams, vice president and fashion director at Neiman Marcus, report that the seven-fold tie, which can measure as much as three-quarters of an inch wider than the average tie, has never been more popular. Really, says Barneys creative director Simon Doonan, “the only faux pas is to wear a tie that misrepresents you.”

No Tie
You wear it if … you run a social networking site and, unless you’re on your way to a meeting with Murdoch, you abide by the dress code of Silicon Valley’s first coming. “When you think about the dotcom days, there was this era of prosperity—but you looked around and people were dressed as if there wasn’t,” says Jeff Blee, merchandise manager of men’s furnishings at Brooks Brothers.

The Extreme Skinny (2.5 inches)
You wear it if … you’re with the band or, more likely, in the band. “It’s your rocker look,” McWilliams says. “It’s a fashion statement, not a power statement.”

The Skinny (2.5 to 2.75 inches)
You wear it if … you manage ad accounts on either coast or run a graphic design business out of your home. “The person who wears the skinny tie to work doesn’t have to wear a tie to work,” says Kalenderian.

The Trimmed Classic (3 to 3.5 inches)
You wear it if … you favor the close-cut, streamlined suits popular with traders—and you’re built more like Larry Ellison than Hank Paulson. “If you have a big man, and he puts on a three-and-a-half-inch tie, he’s going to look terrible,” says Benson.

The Classic (3.75 inches)
You wear it if … you bought five timeless suits when you made partner, and intend to test the lifetime guarantees. “That guy doesn’t want to think about getting dressed in the morning,” says Michael Macko, vice president and men’s fashion director at Saks Fifth Avenue. “He just wants to have ties that match his shirts, ties that match his suits.”

The Luxury Classic (3.75 inches and up)
You wear it if … you’re a tobacco heir, oil baron, or C.E.O.—or you’re trying to get one of them to invest their money with you. The seven-fold tie, popular with menswear mavens, is as much about plumpness as it is about width. Made from a single swath of material, the seven-fold is “for someone who’s probably not afraid to impress,” says Kalenderian. “They like the idea that someone might say, ‘Where did you get that tie?’ It’s a statement of luxury, an artisan product.”