A vocal contingent of parents is bemoaning changes to Costco Wholesale Corp.’s Kirkland Signature diapers after the wholesale retailer switched manufacturers for the popular item in recent months.

The complaints, including a TikTok video with nearly 100,000 likes describing the new diapers as “paper-thin,” highlight the risk for retailers as they lean heavily on lower-priced store brands to lure in penny-pinching consumers.

Labels such as Costco’s Kirkland brand can generate intense shopper loyalty, and they’re often more profitable for the parent company. The flip side, however, is that backlash can be intense when beloved products change. As of Thursday, hundreds of customers had left one-star reviews of the diapers on Costco’s website.

First Quality, a company based in Great Neck, New York, that makes Cuties diapers and other items, recently replaced Kimberly-Clark Corp. as the producer of Costco’s diapers, Bloomberg News previously reported. Costco, which said it doesn’t comment on its manufacturing partners, is in the process of introducing the diapers in its more than 600 stores across the US.

Sylve Rosen-Bernstein, an advertising professional who lives in Queens, New York, said she has bought Kirkland diapers for their lower cost and bulk quantities. But when the manufacturers switched, her 11-month-old son began waking up early out of discomfort due to leaks through the diaper’s material, she said.

“It’s a ‘you have one job’ situation,” she said. “You can’t pee through the front of the diaper.”

‘Thinner and Thinner’

Costco has received feedback from customers via its website and call centers about the new diapers and their thinness, said Lucas Stanuch, an assistant general merchandising manager for the company’s health and beauty departments. While the retailer reviews every comment and responds seriously, the design was created on purpose, he said.

“If you look at the evolution of diapers, they have been getting thinner and thinner,” Stanuch said. Manufacturers are looking to produce thinner versions of diapers, as well as feminine pads, while keeping their absorption capacity equal to or better than standard versions of the products, Stanuch said, and Costco wants to be ahead of the curve on that trend.

He acknowledged that navigating social-media reactions is a challenge, and said Costco started receiving complaints even before the new diapers went on sale. In many cases, feedback was for previous version of the product that’s still selling across Costco’s locations, he added.

Costco hasn’t found any manufacturing issues with new diapers upon review and doesn’t plan to change suppliers. The company expects to finish transitioning supply in the coming months.

The latest diapers are more densely packed into the new box, helping with sustainability efforts and shipping efficiency, according to Stanuch. Removing the diapers from the sleeve and letting them sit out overnight will help them expand, he said.

Not all customers are complaining, of course. Some Reddit commenters and customer reviews say they don’t experience a difference, while others even appreciate the more compact size.

But Soraya Al-Khoury, a teacher and resident of the Seattle metropolitan area, said the new version is less absorbent, and the shape is more rectangular than the previous curvier design that accommodated babies’ “chunky little legs.” Her family is finishing its final sleeve of the new Kirkland diapers before changing to Pampers that she bought at Target Corp.

“It’s really annoying paying more,” she said, adding that her family will now have to make a separate stop to buy diapers. “But I think I was going through twice as many diapers anyway.”

One Costco store in the Midwest has experienced a slightly higher number of returns for its Kirkland diapers recently due to quality issues, an employee said, adding that returns have historically been related to sizing problems. Stanuch acknowledged that the company has seen an uptick in returns, but said that typically happens when products change. The number of returns has started to normalize, he added.

Costco is in touch with its previous and current diaper suppliers about every complaint, Stanuch said. After receiving feedback from customers, the company verifies the exact item that was purchased then examines production samples to ensure quality expectations are met. Employees are encouraging customers to give the diapers another shot, or change the size as going up or down can help with leaks. And the company recently posted a video on its website to explain features of the diaper.

US shoppers have flocked to lower-cost store brands in recent years to save money, prompting retailers to invest further in their variety and quality. Against the backdrop of soft consumer sentiment, private-label items have become more important for retailers to grow sales and grab spending.

Kirkland has been an important driver of growth for Costco, which is known for its ever-changing offering of mega-sized items. The store brand, which generates tens of billions of dollars of sales annually, offers everything from tequila to toilet paper. The company has said it’s typically priced at least 20% below national brands. It isn’t unusual for Costco to swap suppliers for Kirkland products, and the company extensively tests all items.

This story was originally featured on Fortune.com