Amazon.com: Made For Amazon, Battery Base in Black, for Echo (4th generation). Not compatible with previous generations of Echo or Echo Dot (1st Gen, 2nd Gen, or 3rd Gen). : Everything Else
Amazon Echo (2020) review: Small in stature, mighty in sound | Engadget
Amazon Echo Pop review: A $40 colorful smart speaker | CNN Underscored
Amazon Echo Sub review: Exactly what you need for Alexa-powered music | Mashable