Comes in pairs.
ORIGINALLY, THE POTARA (ポタラ, Potara) were earrings to be worn only by Supreme Kais and their apprentices. These mystical earrings are said to come with powerful properties; such as allowing two individuals to fuse, or permitting the wearer to use the Time Rings.
I am hereby proud to present to you my very own custom designed Potara Earring - made available in orange & blue - the power is now in your hands.
Source: Dragon Ball Super episode 66, "Showdown! The Miraculous Power of Unyielding Warriors"