We measure our beads in millimeters because that’s how our bead makers work. Millimeters are also how pearls are measured. So most women are slightly familiar with the concept, just ask one if she prefers a 10mm pearl or an 8mm pearl.
A handy thing to remember is that 1 inch = ~25mm
You need to be a bit careful using the brass gauges. The electronic ones will give you a digital readout. They are more expensive and must be handled more carefully.
The brass gauge is inexpensive, easy to put in your pocket to take to bead shows or bead stores to be sure you are buying the right size.
We recently had a customer who was very unhappy because his 8mm beads were only 6mm. His exact words were
“I bought 8 mm glass beads from you. Measured on a gapper, these beads are 6 mm. What am I suppose to do? I need 8 mm not 6 mm. I am very disappointed. How could you so consistently mess this order up?”
Well it turns out he was misreading the gauge. But we can learn from his mistake.