The WMS 40 PRO presenter sets will get your speech across perfectly. The inconspicuous CK 55 L lavalier microphone is easy to attach. Easy to hide in the user's clothes, the WMS 40 PRO presenter sets provide optimum intelligibility for actors, presenters, or moderators. Ease of use lets you focus on what you have to say. The transmitter operates for 30 hours off a single AA size battery.