The P-623 narrow wall hydrant is a single temperature valve while the P-628 features both hot and cold inlets. With a 3-1/8" depth, these hydrants are designed to fit inside a standard 4" wall and install flush with the outside wall. Both valves offer a variety of installation options, come with a lockable stainless steel box, and have integral shutoffs for simple future maintenance. The PRIER P-623 and P-628 hydrants are built for interior walls and non-freezing climate applications. They are great for healthcare facilities, schools, stadiums and other large recreational areas, the company says.