Center head: To locate center of cylinder with diameter (Ød): 30 - 100mm Accuracy: ±0.15mm Protractor head: To set the blade at desired angle to an edge of a workpiece, and can be used to measure angles Range: 0-180° Accuracy: ±7min. Square head: To set the blade at 90° or 45° to an edge of a workpiece Accuracy: ±8min for 90° square, ±10min for 45° square Blade: Range: 300mm/12", Graduation: 0.5mm and 1/32" on front face, 1mm and1/64" on back face Optional accessory: rigid rule (code 7113)