Come on, admit it. You're pushing 40 -- old enough to have Hula-Hooped as a kid.

And now, your kids are doing it.

The Hula Hoop is back.

Maybe it's not quite like 1958, when 25 million Hula Hoops were sold in a frenzy during the first four months the plastic toy was on store shelves. But sales this year are expected to reach 4 million -- which would double 1987 sales, which doubled 1986 sales.

You get the idea.

"We always sell out of them, especially when it's nice weather," said Sharon Wacenske, a department head at Toys R Us in San Jose. Most of the hoops, she said, are being snapped up by kids under 13.

"And they're so cheap," Wacenske added.

Compared with those electronic toys that cost a day's pay, require batteries every couple of hours and go belly up by the end of the day, Hula Hoops are, indeed, unbelievably inexpensive, selling for about $3.75 apiece.

That's even more of a bargain when you consider that in 1958, Hula Hoops sold for about $3.50 each, according to Wham-O, the San Gabriel, Calif., toy company that makes the Hula Hoop.

"I remember standing in line as a kid at a store in Pennsylvania waiting for Hula Hoops to be delivered," said Dan Roddick, director of sports promotion at Wham-O.

"Now, I'm 40, and I have a 10-year-old," he added. "We'll go out to a Toys R Us, and I'll say, 'Hey, Tyler, come over here for a sec. Here's what I played with as a kid. Try it.'

"Boom. Another sale rings up."

Every seven years, the circular toy that you twirl around your hips makes a comeback, industry analysts say.

Why?

"Well, it's kind of like explaining why there are tides," Wham-O's Roddick said. "They are tied to the moon. That's the reason, but, of course, you don't understand it."

Since Jan. 1, K mart has sold more Hula Hoops than in all of 1987, according to David Wegscheid, a toy buyer for the discount chain.

He ties the Hula Hoop resurgence to an '80s trend -- aerobics -- and to the Super Bowl.

"Aerobic places have been using Hula Hoops in their classes, and then the adults take them home to the kids, who begin playing with them," Wegscheid said.

"And at halftime of the Super Bowl this year, they had a guy with a Hula Hoop," he added. "So now it's seen in an exciting atmosphere. It's trendy."

The guy was Mat Plendel, the 1975 national Hula Hoop champ and aspiring actor who has also strutted his hoop on "The Tonight Show." He'll be seen in commercials promoting the Hula Hoop in April, when a big advertising push is scheduled to begin.