The Scientific Glassblowing Learning Center: Glassblower's Calipers
Groz - Caliper spring o/s 150mm od/6 | Tools4Builders
UEETEK 3 Pcs 4 Inch Caliper Set Rapid Adjust Quick Spring Divider Inside ID Outside OD Calipers Fine Adjustment Measuring Calipers : Amazon.ca: Industrial & Scientific