Easy to use-drag, drop, resize, and scale. The heart of the Radian Flex system is the 4- 9- or 11-slot controller chassis. They use a high-performance enterprise-grade motherboard that connects to a Radian PCIe backplane. The backplane contains 4. 9 or 11 half-length PCIe slots for use with compatible Radian cards including video capture graphics and IP decoding cards.