Empire, True Blue, 16" Combination Square, True Blue, Vials Are Accurate To Within .0005' Per Inch, High Impact Acrylic E-Band Mono Vial Offer Superior Durability, Blade Lock Aligns Blade For Quick & Accurate Adjustment, Heavy Duty Machined Head For Guaranteed Accuracy, Scriber Pin Stored On Board For Convenient Marking Of Materials, Etched Markings.