AEDIKO DC Voltage Display 4pcs Mini Digital Voltmeter 0.28" Voltage Tester Reverse Polarity Protection and Accurate Pressure Measurement（Red/Green/Blue/Yellow)） (Three-Line DC 0-100V)

Perhaps the display is a bit too bright, but for the price I can't complain.Turned out very handy for my small Power-supply, you can find a box to 3D print on Thingiverse searching "DC boost or stepdown converter box with voltmeter"

Pictures in the advert seem to show an adjustable resistor so you can tweak the reading. Unfortunately if it has one it's beneath the display and inaccessible...All gave different readings too. I suppose they're ok to give a rough indication of voltage

Four colours are shown and I expected 1 of each, but only red are supplied. There is no option to turn down voltage on rear as shown. Amazon have been made aware of this. Beware of this item.

Cheap and xheerful; adequate for rough puposes, but no great accuracy. on a 10v reference supply, one module showed 9v89 and the other three showed 9v81. Not too far out, if all you need is a rough indication, - say of battery level - but not accurate enough for much more. Rough and ready at a rough and ready price.

I wanted to use these at 25 V, but I get very hot constant use, so no good 4 me :-(

Work will to put in a vent in your car