During its London launch event for the Huawei Mate 20 and Mate 20 Pro smartphones, Huawei also announced its own storage alternative to microSD.

The Nano Memory card (NM card) is a Huawei invention that offers the same sort of storage as a microSD card but in a smaller form factor. In fact, it is the same shape and size as a nano SIM so can be used with the dual SIM tray on a Mate 20.

Here's what we know about the NM card so far.

How does the NM card work?

We're still yet to get our hands on one, but according to the Huawei London launch event on Tuesday 16 October, the NM card is made by Huawei and is 45 per cent smaller than a conventional microSD card.

The microSD card has been around for "15 years" said Huawei on stage, while the NM card is brand new. It offers similar storage capacities, it seems, to microSD solutions.

HuaweiWhat Is The Huawei Nm Card Used In The Mate 20 Phones image 2

The dual SIM tray in the Mate 20 can have two nano SIMs or one of the sides can sport an NM card instead.

In all other senses the phones should see it as extended storage, just as if it was microSD.

What capacity does an NM card go up to?

We're not sure yet, but in the presentation we were shown a 256GB NM card. We don't know if there will be larger storage sizes in future.

When will they be available to buy?

Again, we are yet to find out retailer information. We are also yet to hear from other storage card companies who might also be selling some.

At present, it seems only the Huawei Mate 20 and Mate 20 Pro phones are compatible, so the rollout might be slow to begin with.