This is a replacement part for the rear center seat belt cover in a 2002 Subaru WRX. When tested it proved to be a snap fit with no modification.
I broke this while fixing my back seat and couldn't find any online through Subaru or otherwise. After designing, printing, and installing my replacement I was able to find the OEM here 64715AE070 on parts.subaru.com.
The author marked this model as their own original creation. Imported from Thingiverse.