Greg, I have the Exact same gauges but Instead of 4, I've got a pair of them on a metal plate size by side. They've worked really well and for the price I've never regretted the purchase. To aleviate the needles pulsing though ( I suspect yours are the same ) mine have inline thumb screws that adjust and lessen the higher than needed vacuum amount thereby preventing any pulsing.
Btw, I originally bought the 4 x murcury gauge but preferred the needle type gauges. Certainly both types seem to work equally as well but I just liked the idea of the needle type.
