The Grainger Approved Therma Level Gauge HDPE is a high-density polyethylene level gauge designed for use with water heaters and boilers. It features a clear, shatter-resistant tube with easy-to-read level markings and a 3/4" NPT fitting. The gauge allows visual monitoring of system water levels and can withstand temperatures up to 200°F. With dimensions of 18" length x 2" width, this durable HDPE construction level gauge provides an economical solution for monitoring water levels in hydronic heating systems.