The MQ-L500, is the best and longest recording device. Like the MQU-350 it is by far one of the best covert audio records on the market today. This Korean made audio recorder is designed by a company who specialises in high quality audio recording equipment. If quality, battery life and reliability are you primary concerns then this is your best choice. This audio recorded features both continuous recording and voice activated recording modes. The unit is small and easy to hide. Place it anywhere in a room and confidentially know that you will capture the conversations you need. MQ-L500 boasts up to 500 hours of recording time on a single charge while still being discreet enough to hide almost anywhere.