Two years ago David Montalvo was peeling the gold sticker from the bill of his latest New Era brand baseball cap when he noticed that it left behind an unsightly residue.

"So I decided to just leave it on," said Montalvo, 23, a Mission District resident. "I think it looks cool - the style. It's the way I wear all my hats now."

Leaving the price and size tags on clothing and accessories has become a popular fixture of hip-hop style. One of the latest additions to the trend is the shiny gold sticker affixed to the top of the visor of a New Era baseball cap. The sticker displays the cap's size, brand and style, the most prevalent being the 59FIFTY - a taller and stiffer cap than the others in the line. The stickers are so popular that New Era's New York retail store keeps on hand extra rolls in every size for customers whose tags may have worn off.

New Era, which is headquartered in Buffalo, N.Y., and once designed hats for Babe Ruth and Joe DiMaggio, is the leading sports-licensed headwear company in the world. It's also been the only brand worn by major-league baseball players since 1991.

The caps have migrated from the field to the street and now retail from $32 for the traditional cap to $1,200 for a limited-edition snakeskin version. The company sold 34 million caps worldwide last year and made $300 million.

New Era's 30 designers, based in New York, have responded to the demand for fresh styles, patterns and materials by creating hundreds of combinations. But catering to a street-wise clientele can be tricky.

Activists in Harlem this summer accused New Era of creating Yankee caps adorned with blue and red bandanas to market them to local gangs who wear those colors. New Era responded by pulling the caps from stores and retail Web sites.

Brian Radko, lead designer for New Era, said the company did not start the sticker trend but certainly welcomes the style.

"It's important to stay relevant," said Radko, an 11-year veteran of the company. "The sticker has itself become a fashion statement - an accessory worn on an accessory."

The public relations dustup on the East Coast hasn't slowed the popularity of the company's caps and stickers in California. Anthony Lucero of San Francisco said he is grateful that New Era has embraced hip-hop style. He also said he won't be ditching the sticker anytime soon.

"A lot of people have come to know me for my hats and the size 7 1/4 sticker," said the 25-year-old father of two boys. "I leave the sticker on to let people know it's authentic New Era. And also to show that it's fresh and new."

The caps, which come fitted in sizes 6 through 8 1/4 (48 to 65.4 centimeters in circumference), are not adjustable. The most popular sizes are 7 to 7 3/4.

Country music comedian Minnie Pearl wore a price tag hanging from her straw hat on stage at the Grand Ole Opry and on the popular TV show "Hee Haw," but it is unlikely she is the source of the cap tag trend. It was probably inspired by musicians on MTV and athletes on television commercials who wore tags in the 1980s and '90s. Robb Willer, assistant professor of sociology at UC Berkeley, said tags and stickers could be viewed as conspicuous consumption, pricey items to flaunt in front of others to "curry favor in their eyes."

"Once it gets started, though, most people probably just do it because they see that people in their reference group already do it," said Willer, who studies altruism, masculinity and collective action.

Chris Carter, who sells hats at Lids on Powell Street, said he advises parents buying caps for their children to leave the stickers in place. "When you buy a white hat that has been sitting on the shelf for a while, it gets dusty," he said, "and if you remove the sticker, it leaves a large white circle."

But Carter added, "a lot of people do it because they see rappers wearing the sticker in music videos."

New Era caps have become such an integral part of hip-hop culture that rapper Lil' Flip wrote a song titled "New Era."

Andreana Clay, assistant professor of sociology at San Francisco State University, said she believes there is a constant interplay between marketers and hip-hop culture "on the ground."

"Where it begins isn't often identifiable," said Clay, who studies hip-hop culture and race and ethnic relations. "It could be the youth, fans or a particular artist, and then it's picked up and becomes the trend that everyone does."

Although New Era is sure to remain popular thanks to its relationship with professional baseball and companies like Burton, X-Large, the Hundreds, Stussy and Alife, the sticker trend has its share of critics.

T.J. Marsh, of Huf in San Francisco, said the fashion magazine Complex and the Web site Hypebeast have featured negative stories about the gold sticker. Some call the trend tacky; others say the sticker lacks originality and purpose.

"It's a fashion statement now," Marsh said. "But it's going away because it has no real meaning. Who cares what your head size is?"