"5 MPH Speed Limit - Watch For Children" Sign By SmartSign | 12" x 18" Aluminum DURABLE ALUMINUM. Signs are made using 63 mil thick aluminum and do not bend easily. They have been proven to outlast the toughest of storms. Signs last 10 years outside. LAMINATED. Signs are laminated for superior outdoor durability, chemical and abrasion resistance. ROUNDED CORNERS. Signs have rounded corners and burr-free corners for safe handling, longer life and a professional appearance. EASY TO INSTALL. Signs have pre-punched and pre-cleared mounting holes for easy installation. Signs mount to U-channel posts, square or round galvanized posts, wooden posts and chain link fences.