- PH3 is the best for measuring thickness. (table hardened)
- PH2 has intermediate bearing. It measures the thickness of rings, pipes, and other bent parts.
- 561-U, 561-US, 561-UG, are good for comparison testing of outside diameter.
- 561-PH3G, 561-PH2G and 561-UG has granite base.
- NOTE: Dial Gauge is not included.