"Threaded" on a jewelry listing doesn't tell you enough. There are two ways to thread a barbell, and only one of them is suitable for a fresh piercing. This guide explains the difference, how to spot each type in the hand, and why the thread size on the listing matters as much as the gauge.
The two designs
Internally threaded
The post is smooth on the outside. A threaded hole is tapped into its end, and the ball or top carries a short threaded pin that screws into it. The only thing that touches tissue is the polished post.
Externally threaded
The threads are cut onto the outside of the post itself, at the end, and the ball has a threaded hole. The threads are exposed. When the post is inserted or removed, those threads pass through the piercing channel.
Why it matters
- Tissue damage. External threads act like a tiny rasp when they pass through a healing fistula. Internal threads never touch tissue.
- Surface finish. A smooth, polished post can be inspected end to end. Threads on the outside are hard to polish and easy to burr.
- Bacteria. Exposed threads are a rough surface next to the piercing. Inside the post, the threads are sealed by the seated end.
- Longevity. External threads wear and strip with every change; internal threads are protected by the post walls.
For those reasons, professional studios run internally threaded or threadless jewelry for initial piercings, and the Association of Professional Piercers' jewelry standards for initial piercings specify internally threaded or threadless designs. Externally threaded jewelry is still common in fashion retail, which is one reason clients arrive with irritated piercings.
How to tell them apart
Unscrew the ball. If the post end is smooth with a hole in the middle, it's internally threaded. If the post end has visible threads and the ball has the hole, it's external. In listings, "internally threaded" should be stated; if a supplier only says "threaded", ask.
Thread sizes
Thread size is separate from gauge, and mixing them up is the most common reason an end won't seat. Our threaded posts and ends state the thread on every listing:
| Thread | Diameter | Typically used on |
|---|---|---|
| 16g thread | 1.2mm | 14g and 16g labrets, barbells, curved bars, most navel curves |
| 20g thread | 0.9mm | 18g posts and some fine 16g dangles and tops |
| 21g thread | 0.8mm | Finer decorative tops on 16g and 18g posts |
An end with a 0.9mm pin will spin loosely in a 1.2mm post; a 1.2mm pin will not enter a 0.9mm post. Check the thread on both parts before mixing brands or ordering ends for existing stock.
Internally threaded versus threadless
Both keep threads away from tissue. Threadless (press fit) holds by pin tension and changes without tools; internally threaded holds by a screw and suits heavier ends, larger gauges and oral piercings. Most studios run both. The full comparison is in our threadless versus threaded guide.
Stocking notes
- Standardize your 14g and 16g threaded drawer on the 16g (1.2mm) thread so posts, barbells, curves and ends interchange.
- Keep 20g-thread ends separate and labelled; they look identical to 16g-thread ends from a foot away.
- When a client brings in externally threaded jewelry from elsewhere, treat it as a reason to sell them a proper post, not a reason to reuse it.
What we stock
All threaded jewelry at West Coast Body Jewelry is internally threaded ASTM F136 titanium, with the thread size stated on every listing. Browse the internally threaded collection, labret posts and straight barbells. For sizing by placement see the gauge and length reference.
Wholesale pricing is visible once your studio account is approved. Apply for a wholesale account; approved accounts receive a $50 credit.
Part of our wholesale titanium body jewelry guide for piercing studios.