Our '600' series gauge line is a high quality line of forged brass case liquid filled gauges. The sturdy brass case adds extra protection along with the glycerin filling which helps dampen the effects of pulsation and vibration, while also perpetually lubricating the movement (and keeping contaminates such as dirt away from all moving parts) which will extend the life of the gauge. This gauge has been specifically designed with heavy industrial applications in mind where rugged designed gauges are required as well as any commercial or industrial application not corrosive to brass and bronze wetted parts and where glycerin filling is suitable for use.