Since the great Lululemon controversy of 2013, sheer leggings have become public enemy #1 in the fitness world.

Brands like Yogasmoga, Lorna Jane, and Gap Fit have been heralding their blackest, most opaque leggings as the antidote to dreaded see-through styles, while in-the-know sweat enthusiasts are perfecting the in-store squat test to ensure they’ll be well covered in downward dog.

But even though there are so many full-coverage options, not everyone is taking the time to seek them out—and no one knows that more than fitness instructors. In fact, when I surveyed 50 of the country’s buzziest trainers and asked the one thing they wish they could tell you, a large majority of the responses revolved around unwittingly transparent leggings.

Whether you’re piking on a Megaformer or dipping it low in barre class, there’s a good chance that you’ve given your instructor a peep show without realizing it. “I know it’s a pain, but everyone needs to check out their butt in the dressing room mirror,” a Flex Studios pro tells me. “Workout pants are, without a doubt, the place to invest in a higher quality product. I think a lot of clients would be embarrassed to find out how often I’ve seen their underwear!”

Before you get too mortified, instructors swear they’ve seen it all and it doesn’t bother them (and there’s no reason anyone should feel sexy-shamed at the gym). But if you are looking to keep those Victoria’s Secret skivvies, well, a secret, turn to styles proven to never go sheer.

Scroll down to see the most opaque leggings you can buy—no squat test necessary.