Serta Perfect Sleep Crib Wedge helps safely elevate baby's head and torso. Ideal for babies with acid reflux or congestion. Fits all cribs and toddler beds. Easy to wipe clean. Features counting sleep embossed design. It comes with a Lulla-Vibe Vibrating Mattress Pad. Pad easily slips under crib mattress and creates gentle, soothing vibrations with the push of a button. A 30 minute timer shuts off gradually so baby is not startled. A three second delay start in the power button helps prevent unintentional activation. Simply press and hold down the power button for three seconds to activate. Press once more to change the speed. It is 100% battery operated so there are no cords or charging stations near your little one. Includes 4 AA batteries.