Aquarium Background 3d Rock Design for 55/75 Gallon Aquarium 48" X 21" in 2 Sections - Easy to Install Background in 2 sections - Easy to install - just slide inside and joint both sections, doesn't float, no silicone required Side edges of background have sponges to avoid fish swimming behind you can hide all your pipes, filters, heaters behind the background No silicone required in most cases, background can be placed over the substrate or direclty on the bottom of real 3D background with structure of rock, boulders, stones