The yellow ribbons are back, but instead of being tied around trees or pinned to lapels they are magnets attached to millions of cars across the country.

The 8-inch-tall magnetic print of a loop of ribbon, inscribed with the words “Support the Troops,” can be placed on any metal part of the car. Drivers in New York City commonly put them above a rear light or next to the license plate, but some put them on doors, next to the windshield, or on the trunk.

One reseller based in Brooklyn,Polsteins.com, said it sells an average of perhaps 40 magnets a day, and occasionally as many as 200. It charges $2.99. An official of the North Carolina company that designed the first of these magnets, Magnet America, said it has been selling 50,000 a week since June.

“We don’t think it was any particular political event,” a co-founder of the company, Dwain Gullion, said. “It was just spreading from the military bases.”

Magnet America designed the yellow-ribbon magnet in 2003 for sale to families of overseas soldiers and sailors. The families resell the magnets to raise money for care packages sent overseas or for expensive intercontinental telephone calls.

Magnet America sells its products on the Internet but doesn’t target the mainstream retail market. That business goes instead to such companies as Imagine This, in Richmond, Va., which said it had invented a flag-printed magnet during the first Gulf War in 1991. The head of that company, Michael Moss, said he’s seen sales of yellow-ribbon magnets jump more than 1,000% since the spring, mostly along the Eastern Seaboard.” For the East, the war on terror is real,” Mr. Moss said.

Imagine This also sells ribbons inscribed with the presidential tickets of each major party. Mr. Moss said he tested their sales potential in July at the Virginia State Fair, where Bush-Cheney magnets outsold Kerry-Edwards by about 4-to-1. In New York, the display of a yellow-ribbon magnet doesn’t signify which candidate the driver supports. “We support our troops, and we want them to come back home soon,” a Queens native with a star-spangled magnet, Kulwant Kaur, said. She plans to vote for Senator Kerry.

Magnets appeal to some drivers more than do bumper stickers or decals because they don’t leave a permanent mark on the car when they’re removed. Then again, maybe they’re too easily removed. “I got my first one two months ago,” a Brooklyn man, Ron Johnson, said, “and it was stolen last week in the city.”