This coin cell battery holder takes 2x CR2032 batteries (not included) giving it a 6V output via the 2mm JST-PH connector.
It's really useful for wearable projects or even small portable builds that need 6V but don't require a huge capacity. You can drop the holder down to 3V by using just one battery and bridging the other slot with some folded tin foil or similar conductive material.
The holder snaps closed and includes a useful on/off switch for on-the-fly power control.
CR2032 batteries are a common format and are easy to come by, and usually offer around 200-220mAh capacity.
CR2032 batteries not included - grab some here!