JBL Bass Pro GO Subwoofer - In-vehicle powered subwoofer & full-range portable Bluetooth® speaker.

Engineered for the ultimate sound experience
JBL BassPro Go is a powered subwoofer designed to easily mount & charge in any vehicle, augmenting the output of full-range speakers at the lowest frequencies, with quick disconnect features to become a portable Bluetooth speaker and keep the party on the go.
With convenient and easy to use controls in or out of the vehicle, BassPro Go allows you to dial-in your music exactly the way you want to hear it.
It also has a convenient safety cover to help protect the speaker when used out of the vehicle and to provide an IPx5 marine rating.

In your car, it's a compact sub, but pop it off its mount and it becomes a powerful full-range Bluetooth speaker.