Cherne® Aluminum Fin Style Deflection gas are designed to be field verified by inspectors without the use of a proving ring. Simply place two fins end-to-end as pictured below (1) and measure the width. Add one inch to the mandrel (2) and you have the outside dimension of the ga. Using this method simplifies the inspector's job of verifying sizes on deflection gas. Cherne® Industries is a global leader in pipe plugs and testing.