According to Techcrunch, the round was led by Vivek Ranadive's new fund, Better Our World Ventures Fund, with participation from Cyan Banister of Founders Fund, Ellen Pao and others.

This comes just a couple of months after Flex raised $1 million from Y Combinator, Amplify.LA and others. Flex plans to use the funding to fine-tune its products and further develop its online tech to better serve customers.

BOW Ventures Fund's investment in Flex is one of the fund's first several investments, though, the fund is not yet ready to disclose the other ones. To be clear, this is the same fund that is affiliated with the University of California. While the focus of the fund is on the research, students and faculty of the UC system, it's not a requirement that every startup the fund backs is affiliated with the UC system.

'As a founder who knows how tough building a company can be, the traits I look for most are passion and grit,' Ranadive said. 'Getting to know Lauren, where she's come from, how she built the company and team, the commitment she's shown to serving women, we saw both those traits in spades, and we're excited to share in her journey.'

Flex is about $20 per cycle -- depending on if you buy one box at a time versus subscribe, and how long and heavy your periods generally are. If you subscribe to a quarterly box, it'll cost you $15 a month. Diva Cups cost about $40 and it's recommended that you replace it at least once a year.

'There are a lot of great companies in this world, but very few that tackle difficult and uncomfortable problems,' Banister said. 'Menstruation is a very real experience that half of the world's population works around. There hasn't been a lot of innovation which makes the experience more comfortable, safer and less error prone while reducing stigma. Something that just about every female will face in their lives should have the brightest minds behind it, and I think the FLEX team is well positioned in that regard to pursue a massive opportunity. Equally important, I tried FLEX and I'm a convert. I immediately ordered for our home and office and I'm relieved to say goodbye to tampons for good.'

It's worth noting that Flex is not the only startup tackling menstruation and feminine hygiene, which is a $15 billion market and one that is expected to reach $42.7 billion by 2022. There's Thinx, the reusable panties that hold up to two tampons worth of liquid, and there used to be Softcup, but Flex bought them back in August. There's also Clue, a period tracking app and monthly tampon subscription services.