O Ring Gag with Nipple Clamps Please note: We have two grades of PVC Material and they are Beginners/Soft Bondage: This PVC is light weight and designed for soft bondage play. It feels light to wear but is not suitable for hardcore/heavy bondage. The average thickness of the PVC Material is 2mm Hardcore/Heavy Bondage: This PVC is thicker and stronger and designed for more experienced or hardcore bondage users. It is heavier to wear and more robust. The average thickness of the PVC Material is 2.5mm Choose the grade that is most appropriate to your use.