Measure units are millimeters, it is about 31 mm in width (from horn to horn).
Mesh is manifold, no holes, no inverted faces, no bad contiguous edges.
Here is two version of the model:
1) OBullHx_Solid.stl Here is the solid version. Inside are two parts, the head and the back part. Both parts together consists of 729448 triangular faces.
2) OBullHx_Hollow.stl Here is the hollow version. It consists of 783244 triangular faces. Wall thickness is about 0.6 mm.
And there is a file for a part that works like a plug.