BTT CB1 is an SBC (Single board computer) module developed as an alternative to Raspberry Pi CM4 and can be used directly mounted on BTT M4P/M8P.
See possibly BTT Pi4B adapter which is used to give BTT CB1 or Raspberry Pi CM4 a Raspberry Pi 4B size and functions
Quad-core 64-bit ARM Cortex-A53 at 1.5 GHz and with 1GB RAM
Supports 4K HDMI video and audio
100Mbps Ethernet and 100Mbps WiFi
Compatible with Linux and Debian
Compatible with Klipper in combination with BTT Manta M4P/M8P
Also see BTT CB1 Heatsink and BTT Pi4B adapter which is used to give BTT CB1 or Raspberry Pi CM4 a Raspberry Pi 4B formfactor and features