Featuring an integrated SM58 microphone cartridge, the BLX2/SM58 Handheld Wireless Microphone Transmitter delivers wireless audio with professional clarity and reliability. The BLX2/SM58 Handheld Wireless Microphone Transmitter works with BLX Wireless Systems. Features: Integrated microphone capsule design - Lightweight, rugged construction - -10 dB gain attenuation - Battery Life Up to 14 hours - Battery Requirements: 2 LR6 AA batteries, 1.5 V, alkaline. Frequency: 518-542 MHz