If you've ever used 3D printing for SketchUp then you have no doubt heard of Solid Inspector.
Great news today if you are running SketchUp 2014 or 2015 because it's been updated with new features and a brand new UI. Check out ThomThom's video below. I've been using it and it works great.
You can download it right now in SketchUp by opening the Extension Warehouse and searching for "Solid Inspector"