I use it for my electric violin (approximately 720 gram). The electric violin that I use is Harley Benton HBV 870FR 4/4 Electric Violin.
The violin size is 4/4, also the shoulder rest t is 4/4, but the shoulder rest is a bit smaller than I think, so doesn't fit to the violin. I added some ring to the shoulder rest to make it longer. Finally it fits my violin. It would be nice if the shoulder rest has a default way to make it longer, so I don't have to figure it out myself to put an additional ring.
At the beginning I don't feel very comfortable with this shoulder rest. But then I set it up to make it fits my shoulder and neck. It's good that I can adjust it to my shoulder. I'm happy that it's easy to set it, compared to my previous wooden shoulder rest that cannot be adjusted at all.