Stitch Fix, the online personal styling and shopping platform, built its brand from catering to women. Now, it wants to broaden into menswear.

For six years, the San Francisco startup has been using fit and style data algorithms alongside customer information to bring a digital personal shopping assistant to women, who, for a $20 per month fee, receive boxes of clothing and accessory items from retail brands and boutiques. The Stitch Fix subscriber then pays for what she keeps from her boxes, which are sent as on-demand as frequently as she wants. Now, with a valuation of $300 million and investors including Baseline Ventures and Benchmark, Stitch Fix is rolling out the same service for men, starting with inventory from 50 brands.

“The main challenge is overriding the existing perception of Stitch Fix as a female-oriented brand,” said Toni Box, senior director of social media and content at PMX Agency. “Photography and messaging is going to be critical in overcoming the existing feminine qualities of both the site content and social media.”

To transition into menswear, in the past year, Stitch Fix has collected data from a beta group of 1,000 men, acquired partnerships with 50 menswear brands, and launched two in-house men’s brands. It also hired a team of 10 Stitch Fix Men team members in preparation for launch. It also launched new social media and branded content platforms specifically targeting a man’s point of view.

Stitch Fix is entering a crowded market. Startups claiming to help men shop have popped up at a fast pace: Trunk Club, Bombfell, Fashion Stork, Five Four Club and Frank & Oak, for instance, all offer a platform that plays on the idea that men are too busy, lazy, distracted or uninterested to shop traditionally for themselves. That idea has gotten some companies some traction — Trunk Club, for instance, was acquired by Nordstrom last year for $350 million — but market saturation and men’s shopping behavior presents a challenge for any company new to the space, even as the menswear market is expected to grow 14.2 percent to $40 billion by 2019.

“For menswear, the differentiation play is the most important at this point. What does one service offer that others don’t?” said Work & Co. partner Jon Jackson. “A lot rides on the digital experience that makes customers feel the most confident. Otherwise, men simply aren’t going to bother.”

Stitch Fix counts its existing algorithm as its point of differentiation, which takes customers’ personal size information and questionnaire answers into consideration. Stitch Fix Men general manager Mike Smith said that for the most part, the service is similar to its women’s counterpart. The biggest difference for men’s was a stronger focus on fit: when approaching the menswear industry, Smith said that perfecting a fit and measurement algorithm for men was the biggest task of the expansion.

We’ve measured every piece of clothing that goes out,” said Smith. “Then, we compare the size of the item with the guy’s measurements, and track how well something sells based on how well it fits. Proper fit is a huge differentiator for us.”

According to Smith, for Stitch Fix, launching a menswear sector meant partnering with the right vendors, gathering enough inventory to scale, building out more warehouse space and hiring and training more stylists. In all, Stitch Fix employs 3,000 stylists and 75 data analysts. The final piece will be securing Stitch Fix as a brand for men, not just women.

“Style is still, for the most part, a passive thing for men,” said Jackson.