"Visitor Parking Only" Sign By SmartSign | 12" x 18" 3M High Intensity Grade Reflective Aluminum 3M AUTHORIZED. Signs use 3M reflective High Intensity Grade film mounted to 63 mil thick aluminum. This assures that signs are durable outside. DURABILITY. 10-year durability backed by a 3M warranty and rustproof aluminum. LAMINATED. Graphics are protected from weather and abuse. Graffiti can be cleaned off. Laminated signs outlast competitive unlaminated or overcoated signs. ROUNDED CORNERS. Signs have rounded corners and burr-free corners for safe handling, longer life and a professional appearance. INSTALLATION. All signs come with 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.