This is a 6" diameter fully customizable Geometry manipulative that can be useful in the teaching and learning about the properties of angles, inscribed angles, central angles, arc lengths, and arc measures. Use with a rubber band or two to discover the relationship between inscribed and central angles . Holes for small nails are equally spaced around the circumference along with one in the center. An STL file of a 6" disk that printed well is also included if you don't want to mess with the customizer.

If planning on using this to complement lessons on the subject, print a classroom set so each student can explore, or at least print enough so that each table group can share one.

Additional materials needed:

rubber bands
small nails ( i used some 5/8" nails I had in my workshop with 0.8mm holes) to tap into holes
hammer

If you like this, check out my other objects, including the non-customizable version of this manipulative at: http://www.thingiverse.com/thing:2179477.

Also, If you want a modification to this design, let me know in the comments and I'll see what I can do.

Updated 3/19/17 - A new version was modeled in Inventor (see the Version 4 STL file, not added to Customizer file yet) that has 24 central angles (15 degrees each) around the whole circle, along with 12 inscribed angles radiating 180 degrees from a single point on the circumference (7.5 degrees each). The intent is to better show the relationship between central angles and inscribed angles.