Telect offers a 4RU 23" mount horizontal cable manager (P/N 025-2400-2023) designed specifically for fiber cable slack management, utilizing Telect's K2 post and gate design.  The cable manager allows for side cable entry and exit as well as above and below cable entry and exit.  The K2 post and gate layout allows for clean storage of excess fiber cable using a loop design that protects the fiber while preventing macro bends.