Last Updated: November 9, 2026
Quick Summary
To size a threadless flatback, you'll need three measurements: gauge (post thickness), wearable length (the straight section through tissue), and top size. For instance, 16g x 6 mm indicates a 1.2 mm thick post with 6 mm of wearable length, with the top chosen separately.
- Measure only the straight section between the flat base and where the top attaches, ignoring the pin.
- The 4 mm base threadless labret post suits most standard placements; the 3 mm base works where space is tight.
- Two individuals with the same piercing placement might require different post lengths due to anatomical variations.
- Replacement tops aren't automatically interchangeable simply because the gauge matches; always check compatibility first.
- Arcana jewellery is supplied clean but not sterilised and is intended for healed, established piercings only.
Table of Contents
- Gauge, Wearable Length and Top Size: What 16g x 6 mm Actually Means
- How to Measure Flatback Jewellery You Already Wear
- Threadless Flatback Post Length: Why Placement Alone Doesn't Decide It
- A Quick Checklist Before You Buy
- Frequently Asked Questions
Gauge, Wearable Length and Top Size: What 16g x 6 mm Actually Means
A threadless flatback post is a two-piece system: a flat-backed post and a separate decorative top that pushes into it. Sizing it correctly means understanding three measurements, not just one.
Gauge refers to post thickness, and I've outlined the conversion to millimetres in my Gauge Conversion Chart. Wearable length is the straight section between the base and the top that passes through your tissue. Top size refers to the width of the decorative end in millimetres.
Gauge Conversion Chart
So, 16g x 6 mm signifies a 1.2 mm thick post with 6 mm of wearable length; the top is selected independently. For general aftercare advice, Australian Government health guidance on body art hygiene provides useful information.
Term |
What It Measures |
Example |
|---|---|---|
Gauge |
Post thickness |
16g = 1.2 mm |
Wearable length |
Straight section through tissue |
6 mm |
Top size |
Width of decorative end |
3 mm gem |
How to Measure Flatback Jewellery You Already Wear
The most reliable method to size a threadless flatback is to measure a post that currently fits you comfortably. Lay it flat and measure only the straight section between the flat base and where the top attaches, ignoring the pin.
My Gauge Conversion Chart translates gauge into millimetres.
Arcana Dark Arts Cauldron threadless flatback
Then, check the actual posts available: the 4 mm base threadless labret post is suitable for most standard placements, while the 3 mm base threadless labret post works better where space is more limited.
Threadless Flatback Post Length: Why Placement Alone Doesn't Decide It
Two people with a helix piercing might need different post lengths because anatomy and the exact placement can significantly affect what fits comfortably. A snug fit and a little extra room each have their trade-offs, so there isn't a single, universally correct choice.
Threadless tops and posts connect via tension: the pin on the top bends slightly and grips inside the post. Replacement tops are not automatically interchangeable just because the gauge matches; always check compatibility before purchasing. For example, see how a threadless bezel set gem top pairs with a matching post.
If you're adjusting the fit yourself, a hemostat jewellery adjustment tool can help you handle the post safely. Bending a threadless pin too far can weaken the grip, potentially causing a top to work loose and fall out without you noticing.
A Quick Checklist Before You Buy
- Confirm your gauge in millimetres.
- Measure the wearable length on a post that fits you well.
- Check your top's pin is compatible with the post brand.
- If you're unsure, ask a practising professional piercer for advice.
Arcana jewellery arrives factory-new and clean, but it is not sterilised. It is intended for healed, established piercings only. It isn't suitable during the first 12 weeks of healing, and reaching 12 weeks doesn't automatically mean a piercing is fully healed. If fit or healing is uncertain, have a practising professional piercer assess it.
Why should the back be boring? My flatback designs carry detail front and back. Summon Your Style, whatever the size.
Sizing a threadless flatback ultimately comes down to three numbers and one honest measurement. If you're unsure, that's a conversation for a professional piercer, not a guess. Arcana Body Jewellery stocks implant-grade titanium posts in multiple base diameters, with threadless tops to match, and every listing states its measurements. Get started with Arcana Body Jewellery and find a flatback that fits properly.
Frequently Asked Questions
How do I know what size threadless flatback I need?
Start with the gauge and wearable length of a post that already fits you well, then measure the post from the flat base to the top of the shaft. If you don't have one to measure, ask a practising professional piercer to assess your fit. Arcana jewellery is supplied clean but not sterilised and is intended for healed, established piercings, so your size should be confirmed before you order.
What does 16g x 6 mm mean on a flatback post?
The 16g refers to the gauge, which is the thickness of the post, and 6 mm is the wearable length, meaning the space between the flat base and the decorative end. It does not describe the size of the top. Reading both numbers together tells you whether the post will sit snugly in your piercing without pressing or leaving excess room.
Are threadless flatback tops and posts interchangeable?
For Arcana pieces sold in gauge-specific versions, match the top to the post: 14g with 14g, and 16g with 16g. Check the product listing for compatibility before mixing pieces from different ranges or brands. Threadless tops stay in place because a slight bend in the pin creates tension inside the post. Even with a compatible post, you may need to gently readjust that bend when swapping tops or posts. If the top feels loose or won’t sit flush, don’t force it. Follow Arcana’s threadless fitting guide or ask a professional piercer to check the fit.
