CR2050 Lithium 3 Volt 290 mAh. Single Battery.
The USPS announced 5.16.12 10 AM EST No international shipments of any lithium batteries are allowed. Please do not order if you are outside the USA.
Fits and replaces: Ergo Basix Acumen Heart Rate Monitor Acumen EON Basix Plus ES Women's Heart Rate Monitor Standard Basix Plus heart monitor Acumen chest transmitter Trim Belt II Pro Acumen Heart Rate Monitor EON Basix