Replace batteries as a single unit in just a few seconds and reduce the risk of losing valuable data. You may find it necessary to replace your PEM2 batteries in the field, and this is best accomplished by changing the battery holder as a single unit. Once you remove the old batteries from the PEM2, you have approximately 20 seconds to replace them before memory is lost and all programming is set to default. If your PEM2 returns to the default settings, data and calibration values will be lost. Batteries not included. $25 each.