Area of a Parallelogram

Prove to yourself that the area of a parallelogram is the base times the height.
Here's an overview video:
http://www.youtube.com/watch?v=wC8gYuBQaK4
Three puzzle sets are provided. Each set can be arranged to form the same rectangle and rearranged to form different parallelograms with the same area.
Teachers: Have students follow the Exploration Guide (pdf file). It asks some good questions to get them thinking mathematically.
Here are the Common Core standards associated with this manipulative: 3.MD.5, 3MD.8 and 4.MD.3
I've included the source files (SketchUp) in a zip archive.