This article originally appeared on Health.

When it comes to beauty products, Birchbox subscribers know their stuff. The retailer’s popular subscription box service sends out a fresh batch of beauty samples every month, so you know longtime subscribers have tried their fair share of makeup, hair, and skincare products. The mascara they rate the absolute best? Benefit They’re Real! Lengthening Mascara ($24; birchbox.com).

With over 34,000 reviews, this mascara is one of the website’s best-selling products of all time. Birchbox reviewers rave about the formula, which beautifully lengthens and separates lashes (without clumping!) and doesn’t smudge, even after a sweaty workout.

“This is my favorite mascara by far,” writes Birchbox user Jenadora. “Only one coat needed. Comes off with cleaning easily. Lengthens. Always receive compliments on this.”

The mascara even has the celebrity makeup artist stamp of approval: in a previous interview with Health, Los Angeles makeup artist Pati Dubroff (her A-list following includes Naomi Watts and Dakota Johnson) told us the buildable formula is one of her go-tos. “You can get major length without that bulky or clumpy look,” she explained.

The only downside? People might have trouble believing you’re not wearing false lashes: “I’ve tried a ton of mascaras in my day and this is the best by far,” says Birchbox user Rockyraweggs. “It almost works too well in that people think I do have on fake lashes.”

The cult favorite comes in black, brown, and blue, so you can choose the shade that best flatters your eye color.

Want more tried-and-true beauty products? Other Birchbox bestsellers include Benefit Gimme Brow Volumizing Fiber Gel ($24; birchbox.com), which has more than 46,000 reviews, and Arrow Boost Color Enhancing Lip Balm ($14; birchbox.com), a high-tech balm that enhances your natural lip color for a subtle pop of color.