Aquatic Technology 5014WS1218E 12"x18" White/Red Danger Spa Closed Sign (Strong Chemicals) Sign measures 12 x 18 inches, is printed on .040 mil Styrene Plastic, and is designed to inform patrons that the spa is closed when strong chemicals are in use in the pool. Our Danger signs indicate an imminently hazardous situation. This sign is lightweight, durable, and waterproof for indoor or outdoor use.