An Ateco half-sphere mold (4930). Official heading is Half Sphere Mold. Holds 4 fl oz. Size 3" diameter, 1.75" high. Stainless steel. Made in China. Store title says Stainless Sphere Mold; the official page and catalog are half sphere. Specs from Ateco's Half Sphere Mold page.
A half-sphere, 3 inches across, 4 fluid ounces. Official name is half sphere.