Amazon quietly launched its own private label diapers on its site last week, this time under the Mama Bear brand. The brand, which already sells other baby items like baby food and diaper pail refills, is now carrying size newborn through size 6 diapers. However, shoppers will have to request an invite to purchase the items, as they’re still being launched.

The arrival of Amazon’s own diaper brand follows reports from last year which claimed Amazon was planning to re-enter this market, after pulling its line of diapers sold under the Amazon Elements name back in January 2015.

While Amazon Elements continues to sell baby wipes, it more recently expanded to include vitamins and supplements – not other baby products.

But the success of Amazon’s baby wipes line may have rival diaper manufacturers fearing Amazon’s return to the market. Today, Amazon Elements wipes have achieved 14 percent market share, up from 9 to 10 percent since last year, notes the firm One Click Retail. Another brand, Water Wipes, have gained more market share in wipes, but Amazon Elements is the number 2 gainer, the firm said.

While still invite-only, Amazon’s new diapers area already proving to be a strong sales driver for the Mama Bear brand. The seven ASINs (Amazon Standard Identification Number, or basically, an Amazon SKU) for these new diapers have now accounted for 38 percent of the brand’s sales.

In addition, Amazon launched a new diaper pail refill ASIN around three months ago. On its own, it accounted for 41 percent of Mama Bear sales last week.

In other words, diapers and the diaper pail refill combined accounted for around 79 percent of Mama Bear sales last week.

While Mama Bear sales have spiked before – such as during Amazon’s sales holiday, Prime Week – the launch of the new private label diapers led to the largest sales spike the brand has ever seen last week, says One Click Retail CEO Spencer Millerberg.

Amazon’s investment in its private label lines has been exploding in recent months, including fashion, home, and other verticals. Its latest additions, reported this week, were new lines of activewear clothing, via brands called Goodsport, Rebel Canyon, and Peak Velocity. It also just entered the furniture market, with brands called Rivet and Stone & Beam, following earlier expansions into lingerie, shoes and handbags, and plus-size fashion.

A number of Amazon’s private labels today have seen millions, or even tens of millions or hundreds of millions in sales. A prior report from One Click Retail found the AmazonBasics line, for example, has over $250 million YTD, or 85 percent of total private brand sales in the U.S.

Meanwhile, Amazon’s apparel label Lark & Ro and its baby care and vitamins brand Amazon Elements have each grown 90 percent year-over-year, with respective sales of approximately $5 million and $10 million, the report said.

The new Mama Bear-branded diapers are being manufactured through Kimberly Clark, a source familiar with the situation says.

The diapers also come in two pattern options, white and a bears print, and are sold as 4-packs, with a varying amount per pack, depending on the diaper size. They’re competitively priced with leading brands: for example, 128 newborn diapers will sell for $25.49 when launched; 216 size 1 diapers are $38.49; 184 size 2 diapers are $39.69; and so on.

For comparison’s sake, 128 newborn Pampers Swaddlers are $26.28 and 216 size 1 Huggies Little Snugglers are $37.04 – to give you an idea of diaper pricing in general.

When comparing four sizes of Pampers Swaddlers that did have exact equivalent pack sizes to Mama Bear’s packs, Amazon’s brand saved shoppers 11 percent to 17 percent.

For Amazon, the addition of its own diapers and other private labels will have a bottom line impact, due to their increased margins. Plus, in some cases, the labels are used to drive customers to subscribe to Prime, as the brands themselves are Prime-only. So far that’s been the case for Mama Bear products, but the diapers aren’t yet labeled this way. However, that could be because they’re still in invite mode.

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