Does your sub need to be taught proper posture and docile attitude? Or do you need to support his neck in some creative positions? Our posture collar made of heavy industrial rubber is what you need.
It acts like a neck brace that keeps the chin upright, and prevents both vertical (top to bottom) and lateral (left to right) movements, so your sub will not be able to nod or shake their head. Make sure that they have other ways to respectfully express their consent or non-consent so that everyone can have fun while teaching them proper attitude!