- Stainless Steel Case And Bezel - Brass Internals & Connection - Phosphor Bronze Bourdon Tube - Plastic Lens Standard - Glycerine Filled The Glycerine Filling 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 the original equipment manufacturers in mind and are typically used on hydraulic & pneumatic systems as well as any commercial or industrial application not corrosive to brass and bronze wetted parts where glycerine filling is suitable for use