The 2178 family includes seven distinct models – XSB, XLB, S, SL, LS, LL, and XL in flame retardant and non-flame-retardant versions with flexibility built-in for growing networks. A full line of closures and accessories designed to protect fiber optic facilities. Use the chart at right to narrow down your optio es that fit most butt/branch splicing configurations. GROWING GROWING TECHNOLOGIES. The 2180 Cable Kit is used when the 2178 Fiber Optic Splice Case is reentered. Tray Base Buffer Tube Tubing 1 Rl. Fusion Splice Holder Dual Lock 3/4" x 3" 3.