The 'tampon replacement' that means you can have mess-free sex during your period.

No longer are tampons and pads your only options for when Auntie Flo drops in.

From the menstrual cup to period underwear, there are plenty of period alternatives that have gained popularity recently. Now, you can add another one to your list.

It’s called the Flex menstrual disc (yes, disc) and it’s described as the “tampon alternative designed to be so comfortable you’ll forget you’re on your period”.

It's a big call.

Created by two women, Lauren Schulte and Erika Jensen, the single use product can apparently be worn safely for up to 12 hours and features an outer edge (or disc) made of a "proprietary blend of medical-grade polymer" which forms to your natural shape through body heat.

The centre is soft so it collects rather than absorbs your flow. It's made to fit inside the vaginal fornix, covering the cervix. Unlike a menstrual cup or tampon, it doesn't sit inside the vagina canal which theoretically means you can have mess-free sex on your period.

So how does it stack up?

Gigi Engle trialled it for Allure and described it as initially "intimidating", and said she screamed through the application.

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"There was no reason for this other than the fact that I was being a wimp. I got a little period blood on my fingers, but that can happen with tampons, too," she wrote.

Once it was in, she said she could barely feel anything. She says the first attempt at "mess-free period sex" didn't go very well.

"Like your vagina would with a kegel ball, the muscles contract around Flex, making penetration difficult. We couldn't get my partner's penis more than halfway in either missionary or cowgirl. He said he could feel something up there, and that it hurt to bang against it," she wrote.

The second time was better, she said.

Menstrual cup bloggers Kim Rosas and Amanda Hearn of Put A Cup In It also weren't totally enamoured.

"Wear was comfortable but removal was anything but. Amanda found it painful to remove and poor Kim ended up in a horror show situation [blood on her fingers] as a result of a moderate flow day," they wrote.

They also called it expensive (US$20, about AU$27 for eight discs) and questioned their benefit for the environment given they are single use, which is a major selling point for menstrual cups.

However both Engle and Jen Noonan for Prevention said they felt the disc eased her cramps although medical experts were divided about whether it was a direct benefit.

Noonan, who had used SoftCup (a cup-disc hybrid) for some years said she "loved Flex from day one".

The Flex is not yet available in Australia, currently only shipping to the US and the UK although expansion is on the cards.