These threadless straight barbells are made from implant-grade titanium. It is ideal for nipple, tongue, or bridge piercings, but in some cases, it can also be used for ears. Using a 4mm threadless flat disc on one end, they can be made into labrets (best used for the lower lip, cheek, Monroe, helix, conch, lobe, and tragus piercings).. All threadless tops from the line will work with this labret style.