The Krueger 16N458 is a liquid level gauge designed for use with hydraulic reservoirs and gear boxes. It features a clear acrylic window with green and red zones for quick visual monitoring of oil level. The gauge has a brass body and is compatible with SAE 10, 20, 30, and 40 weight oils. It has a maximum pressure rating of 100 PSI and temperature range of -40°F to 250°F. The gauge has 1/2" NPT threads for easy installation and its compact 2-1/4" x 2-1/4" size allows it to fit well on most reservoirs. Overall, this is a sturdy, no-frills mechanical gauge for monitoring oil level in hydraulic systems.