There are 4 permitted types of measuring ring in the British Standard.
1-3 look cheap and 4's quite expensive.
Does it matter which is used? And which one does anyone use currently?
Thanks in advance.
- 30mm cylinder 50mm high
- 68mm cylinder 35mm high
- 65mm cylinder 40mm high
- truncated cone, top 70mm diameter, bottom 100mm diameter, 60mm high.
1-3 look cheap and 4's quite expensive.

Does it matter which is used? And which one does anyone use currently?
Thanks in advance.