This is just a basic plug to fill in the handle and create a fully enclosed build chamber. There are some other great design available but I created this one for its simplicity and fitment. I also have another plug design available to fill the hole when the included spools are not used: http://www.thingiverse.com/thing:775823

Note: This is intended to be a tight fit but each machine has different tolerances and you may need to sand down the 6 small tabs along the edge just slightly. For instance, on the left side of my printer the design fit without any modifications, whereas, the right side required minor sanding.

Printed with ABS to withstand higher temperatures and at 0.1mm resolution to provide improved tolerances.