I did a project a while back in which I was cutting some compound angles.  I made do with the clear plastic protractor I had in the shop and it turned out fine but I was thinking there has to be something better than this.  I have one good potractor type device but it's not made for what I was doing so I started looking for something better.  I'm somewhat embarrased to say I was completely unfamiliar with Infra though I've been a "shop guy" for most of my 65 years.  Anyway this tool popped up on Amazon.  I liked what I say and read and ordered it (along with an Incra rule set).  While I have not done a project in which I've had to use this protractor since I got it, I did go back and duplicate what I did on the previous project on paper and scrap wood and it is a fine tool.  I was marking angles along the side of a board and the bar for want of a better word along the bottom puts the protractor right where it needs to be to measure the angles and it's really easy to line up the index marks on the protractor with the point I marked on the board.  All the angles and fractions are clearly marked and the slots cut in the protractor make it easy to mark just where I want to with the included 0.5 mm mechanical pencil.  Like the other Incra tools, it's made from thin stainless steel to make for more accurate marking with no parallex error.  As a result you don't want to just throw this in you tool box with the hammers and pipe wrenches.  It's a precision tool.  I actually made a little wooden box with the protractor and other Incra tools fitted in it.  The tool is US made and that's important to me.