CANADA-WIDE SHIPPING DEALS: $14 flat rate over $150, FREE if over $250 (Exclusions: large equipment, clay, plaster bats, raw materials, orders going to PO boxes)
A cleverly designed caliper. Measure the opening of your thrown pot with the lid master. Tighten the wing nut. Now use the other end for measuring the lid. Both the inside and outside ends of the lid master will always be identical.
