Huawei's Mate 20 phones bring some clever new features to the table, but there's one that you might not be so thrilled about: a proprietary storage format. The new handsets are the first to take NM Card, a Huawei-made design that offers the capacity and performance of microSD in a card the size of a Nano SIM. On the Mate 20 line, this promises flexibility. You can use one of the phone's two SIM slots as extra storage without the need for a dedicated microSD slot or an extra-long tray. Sounds great, right?