Flat Back Post Length: How to Choose, and How to Tell It's Wrong

Why the bar you were pierced with is the wrong one to reorder

This is the single most common mistake, and it is not the customer's fault. A piercer deliberately fits a longer bar than you need, because a fresh piercing swells. That extra length is a temporary allowance, not your size.

Once swelling settles — usually a few weeks to a few months, and only your piercer can confirm — that same bar becomes too long. It rocks, catches on hair and pillows, and applies leverage to the channel every time it moves. Downsizing to your settled length is a normal part of the process, not an upsell.

So if you are reordering by measuring the bar currently in your ear, and that piercing is new, you will order the swelling allowance rather than your actual size.

How to tell your post is too long

• You can see a visible gap between the flat disc and the back of your ear.
• The decorative top sits away from the skin rather than flush against it.
• The piece tilts or rotates on its own during the day.
• It catches on hair, jumpers, towels or headphones.

A bar that is too long is not merely annoying. The extra leverage is a recognised contributor to irritation and to piercings migrating out of position.

Typical settled post length by placement

How to tell your post is too short

• The flat disc leaves a visible indentation or ring in the skin.
• The disc or the top looks like it is sinking into the tissue.
• You feel constant pressure rather than nothing at all.

A post that is too short is more serious than one that is too long, because sustained pressure on tissue is what causes embedding. If a piece feels tight, take it to your piercer rather than waiting.

A correctly sized flat back should be unnoticeable. If you can feel it at all, something is wrong with the fit.

Choosing between 6mm and 8mm

The honest answer is that it depends on the thickness of the tissue, not on personal preference — and tissue thickness varies by placement more than by person.

A helix is thin, so 6mm is usually right once healed. An inner conch is the thickest cartilage in the ear, so 6mm will almost always be too short there and 8mm is the normal answer. A tragus is thinner still, and 5mm or 6mm gives the neatest fit.

If you are between sizes, the safer error is slightly long rather than slightly short. A marginally long post is uncomfortable; a short one presses.

Flat back, butterfly back and screw back

A flat back — sometimes called a labret — has a smooth flat disc that sits against the skin. It is the standard for cartilage because there is nothing protruding to catch, and nothing textured to trap debris.

A butterfly back is the pinched clasp on most lobe earrings. It sticks out, presses into cartilage, and its folds hold moisture and product against a healing channel. It is not suitable for cartilage placements.

Flat backs come in two attachment types: internally threaded, where the top screws into the post, and threadless (push-pin), where the top's bent pin holds by tension. Both present a smooth surface to the channel. Externally threaded posts, where the thread is on the outside of the bar, drag that thread through the tissue on the way in.

Common questions

Sizes and healing times on this page are typical ranges, not guarantees — anatomy varies and healing differs from person to person. Your piercer has seen your piercing and we have not: check with them before changing jewellery, especially on one that is still settling.