The Clammy Ruler 8" 

The Clammy 8in is an innovative multi function template that can be used to cut 8in clamshells, circles, half circles, quarter circles, and orange peel shapes! This is the "new and improved" Clammy 8in which now includes registration marks right on the template for easy transfer to your shapes.

Also available:

6" version of the Clammy Ruler
8" version of the Clammy Ruler
10" version of the Clammy Ruler
12" version of the Clammy Ruler