Modular smartphones may be a bit of a bust, but modular phone cases can still be a clever way to add new features to a regular handset. Mophie’s new Hold Force system hopes to do just that, using a magnetic design that makes it easy to switch between modules on the go.

Hold Force is available now from Mophie and Best Buy for the iPhone 7 and iPhone 7 Plus. To start, you’ll need a “base case,” which puts a magnetic panel on the back while protecting the rest of your device. The case costs $39.95.

Mophie is also offering three Hold Force accessories to start. There’s the Powerstation Plus Mini, which offers a 4,000mAh battery pack that snaps onto the back of your phone magnetically. It comes with a built-in cable that can switch between Lightning or micro-USB ports, which means it works with Android devices, too. It costs $59.95.

You can also grab a $19.95 Hold Force wallet attachment, which adds a couple of pockets for credit cards and IDs on the back of your phone. Finally, there’s a folio accessory for $19.95 that protects your iPhone’s screen and adds three credit card pockets on the inside cover.

Hold Force is limited to a few modules for now, but Mophie could easily add new accessories in the future with almost unlimited possibilities (especially if the company opens its platform up to 3rd-party firms). You can order the cases on Mophie’s website now via the source link below.