The fiber cassette is a modular component of the fiber optic system designed to simplify and organize the connection and management of fiber optic cabling. 40mm splice shrink sleeves, fiber pigtails, and a populated adapter plate. Available in three platforms, you can choose the density and capabilities you require: Opt-X HDX – 144 LC fibers per RU, e2XHD – 96 LC fibers per RU, and Opt-X SDX – 72 LC fibers per RU. And new Leviton Base12 universal polarity cassettes allow for the same interchangeable cassette on both ends of. optic cable, terminations, splices, connectors and patch cords.