Rollbe is the World’s Most Compact Ruler
Rollbe is a compact pocket ruler that allows you to measure just about anything—straight lines or curves. Simply roll from point to point counting full rotations of the rolling wheel and add any remaining units. Made of stainless steel & available in centimeters & inches, with a keychain size 4-inch & 10cm model and larger 8-inch & 20cm model. A funded Kickstarter.