These two parts are from Cerb's most excellent "Articulated Wheatley from Portal 2"! Be sure to go check his model out: https://www.thingiverse.com/thing:2868266
I removed the joint that connects the face to the body on the inside so you can add electronics to move the face instead. These are just two of the parts you'll need to build the entire model, so please visit the link above for the rest of Cerb's files!
If you plan on making Cerb's model life-size, scale everything to 438.47%. This will give the model a diameter of 12 inches.