Speed Limit Enforced By Aircraft 12 x 18 - Road Sign. A Real Sign. 10 Year 3M Warranty REFLECTIVE SHEETING: 3M Engineer Grade reflective sheeting. GAUGE OF ALUMINUM (thickness): 0.063. ALODIZED ALUMINUM: Sign is Manufactured on D.O.T. Alodized Aluminum. BEST PERFORMANCE: Our signs last 7-10 years in Florida UV and sunlight, are washable, completely recyclable, environment friendly. SIZE: 12 x 18.