oil filled pressure gauge help absorb vibration and pressure spikesglycerine is the standard fill fluid and provides performance Production Description 1) Case with rolling2)Dial: 1.5"-6"3) Connection size: 1/8", 1/4", 3/8", 1/2"4) Connection threads: NPT, BSP (G, PF), BSPT (ZG, PT)5) Connection mounting: bottom, top, left, right, center back, offset back6) Liquid filled media:glycerine oil or ...