Kristin Cavallari rocks black string bikini months after revealing runway-ready routine

Kristin Cavallari is soaking up the final stretch of summer while putting her own skin care front and center.

The 39-year-old reality star and entrepreneur wore a black string bikini in a series of new photos promoting her Uncommon Beauty skincare line.

In one of the photos, Cavallari posed beside a sheer white curtain overlooking the water while wearing a black triangle bikini with tie-side bottoms.

She stood facing the camera with one hand resting near her hip and the other holding the curtain. Cavallari wore her shoulder-length blond hair in loose waves as a pool, blue water and distant skyline filled the background.

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"Tan lines, vitamin C + peptides ????☀️," Cavallari captioned the Instagram post.

A second photo captured Cavallari from the side in the same black bikini.

The "Laguna Beach" alum leaned against the curtain with one arm raised above her head as she smiled with her eyes closed. The pool and waterfront setting remained visible behind her.

Cavallari also used the photo shoot to spotlight a product from her Uncommon Beauty line.

In a close-up image, Cavallari leaned against a palm tree while holding a bottle of the brand’s Enhanced Pineapple Peptide Nectar near her face. She continued wearing the black bikini as a large green leaf partially framed the photo.

The latest set of photos comes months after Cavallari stepped onto the runway at Miami Swim Week for Uncommon James’ first runway show.

During a June 23 episode of her "Let’s Be Honest" podcast, "How I Got Runway Ready for Miami Swim Week," Cavallari detailed how she prepared to walk the runway in a swimsuit.

Cavallari explained that she had known about the show for roughly three months and became more disciplined about a month before the event.

"You guys know I'm pretty healthy in general. But then what I did was I sort of like cranked it up a notch at least a month out," she said.

One of the biggest changes involved alcohol.

"So, my point with this is basically in a nutshell I think leading up to Miami I drank twice in like three months," Cavallari said.

The mother of three also discussed how her approach to fitness has evolved over the years, explaining that she no longer puts the same pressure on herself to maintain a rigid workout schedule.

"I have gotten more lax in the last few years about eating and working out. And I think, first of all, I look and feel the best I ever have," she said.

Cavallari said she typically aims for four workouts a week, including three days of full-body weight training and one session on the StairMaster.

However, preparing for Miami Swim Week presented an unexpected challenge after Cavallari said she was dealing with a torn labrum that had been bothering her for months.

"In my head, I was like, ‘I'm trying to get runway bikini ready, and you're telling me I basically can't work out my legs.’ But I did. I took a solid week off of doing anything with my legs," she recalled.

The injury forced Cavallari to pull back on the heavy weights she typically uses, a change she believed worked in her favor ahead of the runway show.

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"I actually think it worked in my favor because I was able to lean up a little bit more than I have, you know, like I was a little bit leaner than I have been in the last couple of years, I think," she said. "And, um, I think it worked in my favor for the runway."

Despite months of preparation, Cavallari admitted she was "so incredibly nervous" before stepping onto the runway.

"And as soon as I got out there, it was just like, OK, it's go time," she said.

Cavallari described the experience as a milestone for both her and her company.

"It really was such a great moment, I think, not only for the company, but for me personally, because I was nervous," she said. "And I love anytime I get out of my comfort zone and I do something that scares me."