Green Sea Urchin Seashells - Natural Color. Measures approx 2"-3" priced each Green Sea Urchin Tests! These unique sea urchins have amazing natural green coloring and a wonderful shape. Each measures between 45-50mm (1 3/4-2 inches) wide. A terrific addition to your shell collection or beach home decor! These shells are nature's creatures and as such, each is unique. Please allow for slight variations in color and patterning.