Seeed’s ReSpeaker 4-Mic Linear Array Kit and 6-Mic Circular Array Kit are extension boards, aka HAT designed for Raspberry Pi. They are designed for AI and voice applications. That means the customer can build a more powerful and flexible voice product with Raspberry Pi that can integrate Amazon Alexa Voice Service and Google Assistant. ReSpeaker 4-Mic Linear Array Kit and 6-Mic Circular Array Kit for Raspberry Pi each consists of two boards, one is voice accessory HAT, another is microphones linear or circular array.