SMI Shellfish Gauge - The SMI Shellfish Gauge provides quick and accurate measurements of your catch. Features a stamped construction with etched markings, and includes the following notches for common shellfish measurements: 5-3/4in, 6in and 6-1/4in crab measurements, 1-1/2in clam measurement and 1-3/16in shrimp carapace measurement. Always check your local shellfish and fishing regulations before taking to the water. Includes notchings for measurements. The SMI Shellfish Gauge is available in plstic or aluminum.