Self-Recordable Sound Module with Motion Sensor Playback. You may program up to two messages and have them playback separately or sequentially. Easily programmable with a MicroSD card, (not included), which loads your messages right onto the unit. No need to keep the MicroSD in the module. Size is 3 1/2" x 2 3/8" x 1". Uses three AA batteries. Alkaline or rechargeable recommended. Two volume settings and high quality sound.