When the little ball pops out of her mouth, that's how you know she's done! Image source: DeviceBondage.com.
Now that's a powerful image of a bondage orgasm! The black straps and the black ballgag and the black dildo mounted on the sex machine and the black background all contrast nicely against the model's pale pink skin to produce a powerful image of bondage in action, and her pose with her head thrown back really sells it. Nice work!