As part of your Evolution Wireless Digital system, the Sennheiser SK wireless body pack transmitter gives you full freedom of motion onstage, in the round, and on the platform. Connect your own lavalier mic, headset mic, or CI 1 instrument cable (each sold separately), and you’re locked and loaded for rock-solid wireless performance. The compact SK body pack clips discreetly onto a belt or slips into a back pocket. A pair of AA batteries nets you up to eight hours of wireless operation. Want to go green and save some green in the process? Connect the optional Sennheiser BA-70 rechargeable lithium-ion battery pack (not included) and get up to 12 hours of performance on a single charge.