Review on 📸 Effortless Picture Hanging with the 10X10X29mm Square Measuring Kit by Rich Ferguson

These values are clearly inaccurate. If you place all ten on the same surface, you'll get very different readings. The only catch is that if you have a more accurate spirit level (from your tool kit, etc.) you can always take a permanent marker to these mini spirit levels and indicate which bubble position corresponds to "flat". I'm doing this with the one level out of 10 that has been calibrated most accurately.