Choose high-quality  Rubber (not latex)  materials, hand-made. 
 
The outer layer is made of harder rubber material, which enhances the sense of restraint and prevents the wearer from turning his head easily. The inner layer is made of soft neoprene material, which is not prone to discomfort when worn for a long time.
 
Please choose the neck size that suits the user. The product comes with a matching copper lock, so no additional purchase is required.