This thingy is a cap to be placed on the exposed pins of a 26-pin (13x2) cable connector (e.g., an IDC cable connector) such as the GPIO connector on the Raspberry Pi. This was originally created to protect the exposed pins of a stacking header (e.g., http://www.adafruit.com/products/1112) used on a Guzunty expansion board (https://github.com/Guzunty/Pi/wiki) to prevent accidental shorts.

This was printed with default "high resolution" settings in MakerWare (i.e., 15% infill, 0.10 layer height, 2 shells). With these settings, it takes ~27min and weighs ~2g.