Artisan Power Cisco 7921G Phone Replacement Battery. Extended Capacity 2000 mAh Cisco 7921G Replacement Extended Capacity Battery. Fully replaces battery number 74-4957-01 and CP-BATT-7921G-EXT. Lithium Ion Rechargeable Battery Pack | 3.7 Volt | 2000 mAh | Cells Made in Japan Longer Lasting: 2000 mAh capacity rating 8% higher than the OEM batteries. Manufactured by Artisan Power, a leader in premium quality replacement battery packs.