Internally threaded jewellery is part of the APP (Association of Professional Piercers) standard for initial piercing jewellery: the part of the jewellery that passes through your skin is smooth, and the threads are on the removable end(s), such as balls, gems, or spikes.
Internally threaded jewellery avoids any possibility of scraping your tissue with sharp threads, which is especially important with fresh piercings.
