I broke the glass of my watch. The jeweler charged $100 for the repair. I looked for watch crystals on eBay, they are around $3 and $3 shipping. Glue costs $4. So I was able to get the parts I needed for less than $10. But I had no idea of my crystal's dimensions in terms of thickness and diameter. I tried using the little metal rulers I had, but I just couldn't feel safe. Crystals are available in 1/2mm increments in diameter and thickness. I couldn't get close enough. I considered "clinching" my measurements (buying sizes smaller or larger than my best guess) but figured it would be the same cost as buying a caliper. I'm glad I have the caliper. I think you know where this story is going. I fixed the clock myself, saved some money and now have a great tool for other projects. When I bought the caliper it was $20 and had no feelers. The total cost of repairing the watch was about $30 plus some of my time. $70 saved