Industry Leading Durability - Our Fire Extinguisher Tags are made of 25 mil thick aluminum with a heavy coat of black, baked-on ink. Our Fire Extinguisher 4-Year Maintenance Tags are not pencil or pen writable. These tags have a write-on surface which accepts writing only from permanent pens. Good for outdoor use, these inspection tags are screen-printed and withstand extreme wear and abrasion. Ideal For Recordkeeping - Tags are great for maintaining periodic inspection records and inventory records. You can use a hole punch to punch out the month of the inspection too for more effective and longer lasting records.