Poor Grandma just had a girdle. Today, if you're a woman who wants to congeal — er, conceal — tummy rolls, or flabby flesh...

Poor Grandma just had a girdle.

Today, if you’re a woman who wants to congeal — er, conceal — tummy rolls, or flabby flesh, you go “Slim Cognito,” use a “Higher Power” or play “Hide & Sleek.”

With fun names, celebrity endorsements and one-word company recognition, Spanx has become the Oprah (who swears by ‘em) of the body-shaping world.

When the Spanx brand first hit the market eight years ago, it began to change the way modern women felt about their undergarments. In short: Minimalist underwear is out. Body-gripping girdle-like structures are in. Even women who slid into size 2s and 4s started wearing Spanx to help smooth, shape and lift everything underneath.

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But trying to choose just the right garment among the dizzying array of Spanx choices can be confusing and frustrating. And Spanx aren’t cheap.

We decided it was time for someone to decode the mysteries of multiple Spanx. We asked four women of various ages and sizes to try three best-selling types of Spanx for a month and tell us what they thought. Here, the results of our investigation.

Footless Spanx,

medium control, $20

What it looks like: This looks like a traditional pair of hose, except they’re cut off just below the knee.

What to wear it with: Pants (and very long skirts).

The good: “Everyone at work thought I had lost weight.”

• “I was able to wear them with open-toed shoes and slacks.”

• “Fairly comfortable.”

The bad: “Because they go far down on the leg (and I’m short), I couldn’t wear them with any of my skirts or dresses.”

• “Itchy like hose.”

• “Makes me feel fatter when I wear it with pants because it’s an extra layer of clothing.”

• “I felt like it gave me a uni-butt when I wore jeans.”

Higher Power Spanx, $38

What it looks like: This starts right under the bustline and covers the entire midriff, ending in something that what looks like bike shorts. Crotch is open.

What to wear it with: Skirts, dresses, even pants (but be sure you have on a long top so people won’t see your Spanx; see tips box).

The good: “Kept me warm in my cold office!”

• “Made me feel more confident in skirts made of thin fabrics.”

The bad: “Kept slipping down during the day. By the end of the day, the top band would be around my waist.”

• “I feel fat putting them on because they’re tight!”

Slim Cognito Seamless Mid-Thigh Bodysuit, $68

What it looks like: Similar shape to the Higher Power Spanx, but this one has a heavier material that holds you in that much tighter. Also made of a slicker material, which keeps clothes draping softly.

What to wear it with: Skirts, dresses.

The good: “Kept me very warm on cold days.”

• “Made my bum look like it was in much better shape.”

• “My husband said, ‘Why don’t you wear that dress more often?’ It’s one I wear all the time, but obviously, I look dramatically better in it with Spanx!”

The bad: “This was so slick that when I wore a skirt, it would slide around my waist and sometimes I’d look down and see my skirt was almost backward.”

• “I really couldn’t breathe comfortably when I had this one in place.”

• “The shorts are long enough on me that if I crossed my legs and was wearing a knee-length dress, someone might see the edge of them.”