The full text for this Euro Truck Simulator 2 (ETS2) mod typically refers to a customization pack designed specifically for the Scania RJL mod and the default Scania R & S 2009 models. The common description for this type of mod includes:
Adds custom, often paintable or chrome, "plates" or "strips" that sit on top of the side skirts. Installation: Download the .scs file. SIDESKIRTS PLATE FOR ALL SCANIA RJL ET R/S 2009...
Requires the RJL Scania Mod to be active if you are using it on those specific truck chassis. The full text for this Euro Truck Simulator