Make sure all your lobster catches are keepers! The Trident Aluminum Lobster Gauge is a corrosion-resistant lobster caliper gauge, and is the legal type required by most Fish and Game Departments. Measuring in most cases is accomplished by measuring from between the lobster's eye sockets to the end of the carapace (Body). Gauge measures 3.25" Legal Sized California Lobster's. Eyelet is provided for attachment of lanyard on end of gauge. Consult local regulations pertaining use and function.