The PolyStack is a modular, stackable, flight controller system for quadcopter / multirotor. The flight controller can be either F3 or F4. Modules are available for common components such as FrSky X4R-SB, D4R-II, MinimOSD, Blackbox Logging, and so forth. Support is currently present for Cleanflight and Betaflight. Support for Raceflight on the F4 board may come at a future date, but is not currently present.
This product is expected to be released in the late July, 2016 time frame. For more information: https://chickadee.tech/