Non-Autoclavable Clear Nose Retainer with Cone end. Thickness 18GA (1mm). Body Piercing Retainers are made of Bio-Flex which is a bio-compatible and hypo-allergenic plastic. Bio-Flex plastic piercing retainers are flexible, light and very adjustable for easy fitting; because of the materials transparency, wearers can easily hide piercing holes. People typically utilize this material where piercings are restricted such as school or work, and for situations like X-ray exams, during pregnancies and while playing sports.