The Ultrasonic Doppler is used to detect heartbeats in fetal puppies at 50 - 55 days gestation. It is a relatively small device and comes with 2 ultrasound gels. It can be fairly accurate and can avoid costly ultrasounds or x-rays. I used this when I was breeding toy poodles. It is in excellent condition with complete instructions and from a smoke free home. Was $185 New - I have the receipt $60 Thanks! :)