Genuine Savi W440, Savi W440-M, Savi W740, Savi W740-M, Plantronics CS540 OEM Replacement Battery or Spare Battery.

Features: 

* Easy to install, just slide the old one off and snap new one on

* Provides up to 7 hours talk time on a full charge

* Full charge takes 3 hours (charge approximately 20 minutes prior to the first use)

* Approximately 1 1/4" x 7/8" x 1/4" thick