Abstract: A wearable device for measuring lobsters includes a metal band encapsulated within a flexible coating to form an elongated body, and a slot defined within the elongated body by a first corner and a spaced apart second corner along a bottom side of the elongated body. The first corner and the second corner extend inwards from the bottom side and into the elongated body, and the first corner and the second corner are spaced apart from each other a distance corresponding to a pre-determined length of a carapace of a lobster. In addition, a cross section of the metal band switches from convex to concave upon changing from a flat position to a curled position when slapped across a wrist or other object.