This device features 4 ultrasonic emitters for 450% greater efficiency in behavior modification. It charges in 2-3 hours with a 1000mAh battery, offering 120 days of standby time. Advanced control includes an 8-second ultrasonic auto-shutoff and a hold function for extended whistle and strobe use. The price drops from $39.99 to just $17.99. Shipping is free for Prime members. Else, it adds $6.