Rose gold plated feather cartilage earring

Rose gold plated sterling silver feather design (11mm long) on a 316L surgical steel 6mm or 8mm bar with 3mm screw-on ball closure secured at the back of the ear.

Which ear?
The feather stud is designed to follow the curve of the ear so it comes in a left and right ear version. Please select the ear that the earring is for. So if you have your left ear pierced you'd need the left ear stud. The one exception to this is front/forward helix piercings where you will need to select the opposite ear for the earring to follow the curve correctly.

Post length Cartilage studs are not adjustable so you need to choose the length of the post.
How do I work out the length?