Original and correct fit replacement battery for the Tesco ARC211 cordless telephone with an answer machine. This Tesco phone battery 2.4V 550-800mAh rechargeable NiMh battery is the exact fit and has the correct plug for the Tesco ARC 211 phone. If you have the ARC211 Twin or ARC211 Triple sets don't forget to increase the quantity of batteries you may need. When you replace the batteries in your Tesco ARC21 phones, carefully plug in the connector and tuck in the wires and replace the cover. Then place the phone on the charger base and charge the new battery for at least 20 hours the first time you charge them.