Review on Enhanced Precision Dividers Calipers Compass for Toolmakers: A Comprehensive Tool for Accurate Measurements by John Holliday

These are fairly simple devices used when precision is required. fully closed, fully open and all points in between. My arms weren't even remotely aligned. the pink plastic I bought for my daughter in the school supplies department of our small town grocery store was better aligned than this "toolmaker's precision compass". And it only cost $1.99. Don't waste your money on this compass. Unless you want to make crooked alignment tools.