It is a sticky Friday afternoon, and Masters Tuxedo in Arlington hums with young men and insistent questions:

"How are these pants supposed to fit?"

"Where do you put the cummerbund?"

"Do you wear a wing-tip collar in or out?"

Just hours before the prom, seniors from nearby Wakefield High School clog the store. Cory Redick's pants don't fit. There is a spot on Tim Wilson's bow tie. For a moment, a salesman cannot find the order for Michael Pickett's black tuxedo.

For a moment, nothing is more important.

Wakefield students, clad in shorts and sneakers, have dressed down to come and dress up, stretching to extremes this one-night contrast -- from T-shirts to tail coats, dirty Adidases to gleaming black shoes, teen-ager to adult.

"I'm not really used to this," says Rick Norton, 18. "I mean, we have dates, homecomings and things, but nothing as extravagant as the prom. But it's fun -- you get to be an adult a little bit. Dress up. Go out to dinner and pick up the check."

"I figure, you only graduate once," says Chris Leach, 18. "It's like, 12 years of school, four years of high school. I figure, you may as well go out in style."

Leach is getting the works -- white tail coat, lavender cummerbund and tie, white top hat, cane, white gloves. His friend, Tim Wilson, is getting the same.

"We should get the band to play 'Puttin' on the Ritz' and get our canes and dance," Leach tells Wilson.

"Here you have a nice combination -- a white tux with a lavender cummerbund," says Terence Aselford, director of advertising and promotion. "The colored cummerbunds are quite popular."

Store manager Jonathan Bovee scurries among the customers, a white plastic tape measure looped around his neck, a big grin on his face.

"I think a lot of it is . . . they want to outdo their friends."

With a month until graduation, these seniors are on the brink of something. They sense, perhaps, that they may be changing more than their clothes. They need to be noticed -- but not too much.

"I got a traditional black tux with a pink tie and cummerbund," says Norton, a thin, freckled senior wearing white shorts and a yellow shirt.

"The pink I did just to be a little different. But the traditional because I was intimidated to get anything too out of the ordinary," he says.

In a calculus of dress peculiar to high school proms, a white top hat and cane are different, but acceptably so. The same for a petal-pink cummerbund. The rented shoes -- shiny patent galoshes -- are just weird.

"I got the shoes. I don't think I'm going to wear 'em, though," says Redick.

Employes at Masters said the choices -- tail coat or dinner jacket, wing-tip collar or not, a simple $35 model or the full works for $65 -- can bewilder young men for whom a tough apparel decision usually means which T-shirt to wear.

"Some of 'em will come in and know what they want," says Bovee. "Some of 'em will come in and their mothers know what they want. Some, their girlfriends have decided what they want."

"The ones with their girlfriends, that's the worst kind," says Renee Tyler, 18, a Wakefield senior who works at Masters. "They get upset." She mimics, whining, "You don't have the color cummerbund I want; it doesn't match my dre-essss . . . . " Tyler's date will wear a white Bill Blass dinner jacket, royal blue cummerbund and black pleated pants. Her dress is royal blue.

"I chose both of them," she says.

Wilson emerges from the dressing room, barefoot, his white tail coat buttoned over a cutoff gray T-shirt and a pair of blue and black shorts.

"You're not supposed to button it," says Leach.

Other prom accoutrements are equally baffling. "The flowers -- I got those this afternoon," says Benjamin Hay, 17.

"I just told the flower shop, 'She's got a pink dress. Suggest something, please.' I don't know anything about flowers."

"I got an orchid -- you know, the one that goes around your wrist," says Leach.

"I got a white rose that pins on," says Wilson. He needs to try on the shoes. "Hey, let me borrow your socks for a minute."

Finally, the salesman locates Pickett's order.

"My tux is black, with long tails, with a white cummerbund and white bow tie," says Pickett. "And black leather, shiny shoes. You can see yourself in them."

As for the flowers, he says, "I got a . . . uh . . . . " He gropes for the word, curling two fingers around his left arm.

"Wrist corsage," says Norton.

"Right. With carnations. One red and two white."

While Pickett waits, Norton models select pieces of his tux -- the black tail coat over his yellow shirt, the pink cummerbund held waist-high. He puts on a pair of very dark sunglasses and faces the mirror.

Behind the counter, Bovee watches and grins. "Prom kids really are more fun than any other customer. They're not quite as jaded as the people who are getting married."