# Pixhawk Autopilot Bus & Carriers
The Pixhawk Autopilot Bus (PAB) Standard (opens new window) provides a standard interface design that allows any compliant Pixhawk flight controller to be used "plug-and-play" with any compliant base board.
This modularity makes it easier to integrate flight controllers into different system-on-module designs. For example, the PAB means that you can use the same flight controller hardware on a more compact board with fewer outputs, or on a board that integrates with a companion computer, and so on.
The following carriers and flight controllers are PAB-compliant, and can therefore be used interchangeably.
The "Mechanical Design" section of the standard provides specific recommendations for mechanical compatibility between vendors. The flight controllers and baseports listed here are expected to be compliant with all recommendations.
# PAB Compatible Carriers
- ARK Electronics Pixhawk Autopilot Bus Carrier
- Holybro Pixhawk RPi CM4 Baseboard (Integrated Companion/Flight Controller Board)