A sports bra and matching legging from Carbon38's second collection.

Activewear e-tailer Carbon38 is doubling down on its in-house line.

The two-and-a-half-year-old Web site recently brought in four additional staffers to help mange and grow the private label business, which launched last year and has topped internal expectations.

However, the site also plans to stay true to its roots and continue selling a wide range of athletic brands. It carries about 80 labels, including Alala, Vimmia, Terez, Alo Yoga, Normal Kamali, Michi, Mara Hoffman, The Upside and Splits59 among them.

“We see that activewear is being redefined, but with that, the definition of ready-to-wear is also being defined,” said Caroline Gogolak, cofounder of Carbon38. “This speaks to how one’s wardrobe is changing and it’s something we’ll continue to build.”

The first in-house designed pieces — a C38 Basics collection that launched on Carbon38.com in November followed by a complete fashion ath-leisure range in December — far exceeded sales expectations, according Gogolak.

Carbon38 released its second collection last week and plans to release additional collections in June, September and November with supplemental deliveries and capsules hitting the site in between the main shipments. At the onset, Gogolak planned to release three main collections per year, but because of early success, increased this to four. The C38 Basics line will expand its offerings as well, and a designer collaboration for holiday is in the works for the fashion range.

Katie Warner Johnson, cofounder of Carbon38, said customer feedback since launch has enabled her and Gogolak to develop a product “that fits — literally — all of her needs.” For instance, she said the line’s leggings have evolved and now have a wider crotch gusset as well as less fabric in the hip area and under the butt.

“That little cinch at the widest part of the thigh gives your butt a lift,” Warner Johnson said of the $115 Zoom compression leggings that come in a graphic magnolia or white and blue based “fluid” print.

While the first collection was well received, Warner Johsnon said adjustments were made to improve the fit, such as a slightly higher waistband on pants and an additional A-line dress silhouette.

That said, the two contend that the site will remain largely a multibrand destination for activewear online, with the majority of sales coming from wholesale partners sold on the site. A conservative allocation for private label in 2016 will be five to six percent of overall sales, she said.

“We’re all about the platform, and creating a dynamic platform that will continually serve our customer. She wants newness on a daily basis, and our private label fills in the gap in terms of where the current assortment is,” Gogolak said.

Industry sources estimate that the site will do about $20 million in sales this year, up from $10 million last year. The venture has raised $5 million to date.