The RK5000PS-3U rack mount chassis supports fiber optic modules. The chassis has 12 slots and an internal double-width power supply. You can insert up to 12 single-width modules or a combination of single-width and double-width modules into the slots. For redundancy, you can use the optional external power supply (EPS5000-120). It provides redundant power for up to two fully populated RK5000PS-3U chassis. You can mount the chassis, which is 3 rack units (RU) high, into an EIA-standard, 19-inch rack. The RK5000-3U chassis has 14 slots and requires an external power supply. You can insert up to 14 single-width modules or a combination of single-width and double-width modules into the slots. You can mount the chassis, which is 3 rack units (RU) high, into an EIA-standard, 19-inch rack. You can use the optional EPS5000-120 external power supply, which consists of dual 120 watt, hot swappable power supplies, to power up to two fully populated RK5000-3U chassis.