Amazon.com : D.O.T. Labels - Hazard Class 2 DOT Flammable Gas Hazmat Labels 4" X 4" Square Stickers - 500 Adhesive Labels Per Roll, Made in The USA by Kenco (1) : Office Products
HAZMAT Shipping Safety Guide | USPS Delivers
4" x 4" Permanent Durable Square D.O.T. Hazard Labels, Hazard Class 5.