This article is from the Piercing FAQ, by Anne Greenblatt with numerous contributions by others.
The names beadless ring and seamless ring are misnomers because the
ring does have a seam where the flat ends of the ring are pushed
together to close the ring. Seamless rings must be torqued / twisted
sideways to be opened and closed. If the ring is opened and closed
frequently it can become warped or break, particularly if the ring is
not annealed.
Seamless rings are not appropriate for new piercings for several
reasons. Inserting seamless rings into a new piercing can be very
uncomfortable and difficult because the ends are not rounded. Closing
seamless rings and aligning the ends is difficult, particularly with
thicker gauges, smaller diameters and harder metals. If the ends are
not aligned the edges will irritate the piercing when the seam rotates
through the piercing. The seam collects bacteria.
Seamless rings made of gold can be made with a rounded convex end and
a concave end which interlock. The convex end should be inserted into
the piercing.
 
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