Keeping up with the laws of what can be taken home, and what needs to go back overboard, is why gauges or rulers are so important. That is why Danielson came up this three-in-one gauge, to keep you worry free, and doing what you love! Quick and accurate way to measure your catch Notched to measure crab shells at: 5-3/4 6 6-1/4 1-1/2 ring to easily identify minimum clam shell size 1-3/16 shrimp carapace measure Diagrams the gender for easy identification Hole for attaching a lanyard