One of the things for guys to consider when buying a flow tool is the type of gauges being used. Gauges are rated a couple of ways and most are rated by the % of accuracy as well as the accuracy at what points in the scale. Some are rated by each 1/3 of the scale being most accurate in the middle, and some thru the entire scale.
The gauge we use is .25% accurate thru the entire scale. This is one of the reasons ours cost a little more then some. It also has a removeable face to reset zero. In this picture it's off zero because it's laying on it's back for the pic.
Just thought I'd share as well so maybe it would help others understand why the little 1 1/2 gauges aren't a good idea... Thanks, SJ