The Giffin Lidmaster does the work of two standard calipers. Make one measurement and have its opposite immediately. In addition, changing the Lidmaster pivot point gives a built-in 12-1/2% differential for making new lids for old pots.
The Large Lidmater functions in the same way as a regular Lid Master (G-LM1), but it allows you to work with larger pots -- up to 20 inches or 50.8 cm in diameter.
For smaller pots, see G-LM1.