321 (SR616) Watch Batteries
The 321 battery is a button cell manufactured with silver oxide chemistry. It is a mid-size, mid-capacity cell used in watches from many manufacturers. Batteries the 321 replaces include the SR616SW, SR65, RW321, D321, V321(540), 28073, SB-AF/DF and SR616.
These 1.55V batteries have a case that measures 6.8mm in diameter x 1.6mm in height. Their capacity is normally about 15mAh.