Honestly, these gauges are the worst gauges made. We got a shipment of 20 into my shop. We had 14 of these gauges blow. The gauges ranged from 0-300 all the way to 0-5000 and everything inbetween. The gauges seem to be very cheaply made, and aren't all that accurate. Personally, I will never use these gauges again.
Go get ashcroft gauges, they are more accurate and actually work.