Four years ago, Michlene Ragsdale, a mother of twins, was as far away from show business as you could get. Then she became president of her local twins club and started getting phone calls from casting directors.

“I’d call all my friends with twins and get their children jobs,” says Ragsdale.

“I then started paying attention to the fact that twins were something in demand.”

Today, that “demand” has turned into a thriving and unique business.

Ragsdale believes she may be the only talent manager in the country specializing in twins. As the owner of Carbon Copies in Mission Viejo, Ragsdale manages more than 200 sets of twins, plus a few single siblings of twins. Her clients appear in numerous commercials, television movies, soap operas, and such films as “Grand Canyon” and “Dragon: The Bruce Lee Story.”

“When I started, I could not believe the reception I got,” says Ragsdale. “For casting directors, it was such a relief to go to one place, rather than call several managers who represented a few twins along with their other clients.”

Twins are a hot commodity from two weeks after birth to about the age of three years, because they enable production studios to double their filming time.

California child labor laws dictate that near-newborns to age six months can remain on the set for up to two hours, and be filmed for 20 minutes.

(At this age, fraternal twins of the same or different sex can work as identical twins, because they are fairly indistinguishable. After that, they need to be submitted as singles.)

“Fifteen days to three months is a prime age,” says Ragsdale. “It goes by quickly, so there is always a demand for more newborns. Also now, there seem to be a lot of birth scenes, particularly in the soaps.”

There’s usually a lull in work for babies ages three to six months, after which they can work longer. From six months to two years, children can spend up to four hours on the set and be filmed for two hours.

From ages two to six years, they can spend up to six hours on the set and film for three. And from ages six to nine, they can spend up to eight hours on the set and four hours filming during a school day, and up to six hours filming while on vacation.

“Ninety-five percent of my newborn twins work, but its seems to get harder from age three on, when they begin competing with singles,” says Ragsdale. “But under age two, the twins have it way over everyone.”

As a result, many agents and managers rarely consider taking on single babies as clients. “When parents call me for representation, I tell them I’m looking for children ages four and older, unless they are identical twins and triplets,” says Meredith Fine, an agent who heads Coast Kids, the children’s division of Coast to Coast Talent Group in North Hollywood, and who specializes in handling twins.

The good news is that twins have come to be used for reasons other than just a way to extend filming. “In the past, twins were more in demand theatrically than for commercials, which tended to hire several babies, film them one at a time, then pick one. Now, more commercials and TV shows are using twins as twins and asking for them in the breakdowns,” says Ragsdale, adding that boy twins seem to be hotter than girl twins right now.

Ragsdale primarily works with five agencies: Coast to Coast, the Savage Agency, the Harry Gold Agency, the Herb Tannen Agency, the Colleen Cler Talent Agency and the Susan Crow Agency.

Because of the short amount of time that twins are at a premium age for work, it’s important that they have managers toremind the agents to submit them for upcoming roles. Very young children, particularly newborns, change dramatically in a few month’s time, so losing them in a file for even a few months wastes valuable working time.

Conversely, agents are more likely to call managers for clients than contact parents or consult their files, because one phone call can get them many potential clients. It’s especially the case with twins, because they are in the minority.

“When I need young kids, it’s easier to call managers,” says Fine, whose twins appear on commercials, such TV shows as “Full House” and “General Hospital ,” and films like the upcoming “The Flintstones.”

“It’s difficult to take on a 2-year-old and talk to its parents every few weeks,” she adds. “I don’t have time to explain to a parent with a single 6 -month-old, ‘There are exceptional singles, but most studios want twins.’ ”

Also, both identical and fraternal twins tend to look and act more alike when they’re very young. While twins sometimes have trouble auditioning without their sibling as they get older, usually the case is that they are determined to become separate personalities.

“I always ask parents if they have a problem with their twins being sent out separately,” says Ragsdale. “I have a couple of moms saying they don’t want kids sent out on their own because their kids don’t do well by themselves. But as they get older, usually one likes to audition more than the other. I’ve had instances where one gets a job and the other doesn’t, which makes the one who’s not quite into it suddenly become interested again. Sometimes, they take turns auditioning or being filmed first.

“There’s a change with teens and pre-teens,” she adds. “At those ages, they don’t like to be known as twins. They develop different personalities, cut their hair differently, one might get heavier. Also, there are very few calls for adult twins.”

Adds Fine: “It goes in stages. Twins can be working well and hit two years old and then they won’t do it. As they get older, their personalities begin to differ. One outshines the other or one wants to audition, while the other doesn’t. They often go through a shy period. Twins differ from singles in that they have each other all the time, so many don’t become outgoing enough. Some casting agents think they get more pizazz from a single.”

During the times her clients run through these phases, it helps Ragsdale to have had first-hand experience. While her twins, now 14, are fraternal–a boy and a girl–they have acted professionally themselves and experienced growing pains similar to those of identical twins.

“I know what it was like when my twins were babies,” she says. “So I know what my clients and their parents go through.”