The labret jewelry has a plate on the inside that prevents it from rubbing against the gums. This type of jewelry is very easy to vary by simply changing the ball. You will find many options in the category "Loose Balls etc."
You measure a labret jewelry between the plate and the ball, only the bar itself should be measured, neither the plate, ball nor threads should be included.
There are several options when it comes to the threading of the jewelry: Externally threaded, Internally threaded, Threadless (completely without threads) Perfect Fit and Push Fit. Be sure to choose the same thread on the stud and top!
On externally threaded jewelry, the thread is on the bar and screwed into the hollow ball.
On internally threaded jewelry, the bar is hollow and the ball has a threaded pin that is threaded into the bar.
On Threadless jewelry, no part of the jewelry has any threads, you push the small pin at the top into the rod about 1/3, angle it a little so that there is a small bend on the pin and push it all the way into the rod and it stays in place.
Perfect Fit jewelry has a combination of a smooth pin and internal thread.
Push Fit is only available on Bioplats jewelry, it is small grooves on the pin that attach to a hole in the stud.