Measure with Precision - The 505A-12 is a 300mm (12") Plastic Miter Protractor that is made from aluminum that has markings which provide accurate angle calculations for precise operation. Easy To Use - Starret protractors are an easy-to-use cutting guide for carpenters, plumbing, builders, and DIY home improvement jobs. It has two laser engraved scales and a smooth pivot assembly for precise operation. Miter Cut & Single Cut Transfers - Our protractors offer miter cut scale transfer readings which go directly to the miter saw for miter joints and single cut scale transfers readings for butt joints. Everything You Need - Cut down your work time and reduce waste by using Starrett's top of the line protractor. It's durable scratch resistant design is ideal for any workplace and construction job. Measure Right The First Time - Our protractors will simply set your saw to the right angle. Upside down or backward, rest assured that you will always get the correct reading.