When properly installed at the oil reservoir drain port, the Xtract™ Oil Sight Glass & Level Monitor allows the user to view the oil color, clarity and accumulation of water or other contaminants. The strong, clear cast acrylic body allows for viewing of the level. The spring-loaded drain valve is positioned to quickly discharge any water before it damages the oil lubricity. Red and green decals are included with the OSGL to mark upper and lower limits, or to designate running oil level and idle oil level. Each Xtract™ Oil Sight Glass & Level Monitor comes with a 2-micron breather, which allows the oil level to equalize with the level inside the system. If you require a closed loop system, install the OSGL without the breather and use the top opening to port back into your equipment.