I like this square, but the Lee Valley equivalent is better than the Starrett. It is easier to read because of the matt finish on the steel. The Lee Valley square slides easier and is slightly larger and thicker as well.

I really liked this small square as I can carry it in my apron and use it on small hard to reach jobs. I have bigger squares, but They are not as easy to use. Starrett 13A Double Square with hardened Blade

You cannot beat Starrett for looks and quality.
Why settle for anything but the best! True it is not cheap. So I buy them one at a time. But for complete satisfaction in in quality then you better go Starrett. I like the 4 inch double square better then the 6 inch only because 90% of the time it does everything I need and it is easier to carry around in my shop apron. There is no play in the action. It is tight and completely square.
If you like tools at all then I would not go any other way.

It's accurate, handy (fits in my apron pocket). what more can I say. Worth the money

I am a professional cabinetmaker and I would highly recommend this tool for anyone that needs accurate layout and checking machines for square. I have had other squares that were adequate, but this tool is the best there is.