FX Indoor, Distribution Tight Buffer, OM4, 12 Fibers, OFNP, Non-Unitized, Red Jacket. Tight-Buffered Fiber Cables are one of Belden’s best-selling, most popular fiber cabling systems for enterprise applications, including intra-building backbones and horizontal and vertical installations. They’re available in fiber counts ranging from two to 144 and designed for indoor and indoor/outdoor applications. Distribution cables are offered in plenum and riser versions for flame resistance, as well as in unitized and non-unitized constructions that fit a wide array of environments. Their 900 µm tight-buffered fibers allow for fast installation and easy termination with FiberExpress (FX) Fusion Splice-On Connectors.