The OPGW cable design is constructed of a fiber optic core (with multiple subunits depending on the fiber count) enclosed in a sealed hardened aluminum tube with a cover of one or more layers of steel and / or alloy wires. The installation is very similar to the process used to install the conductors, although care should be taken to use the appropriate pulley or pulley sizes to not cause damage or crush the cable. After installation, when the cable is ready to be spliced, the cables are cut by exposing the central aluminum tube which can be easily cut with a pipe cutting tool. Color-coded subunits are preferred by most users because they make the preparation of the junction box very simple.