AA battery holder (3 x AA).
Can be retrofitted to existing TankMate v2 units - as an alternative to the C-size lithium battery. Typical lifespan: 12 months (with 3 x Alkanaline batteries)
Can be used with the following battery types (not included):
AA Alkaline 1.5V - (NOT the heavy duty type)
AA NiMH (rechargeable) 1.2V