When ordering from the vendor 'KP Products' beware.  They do not warranty the included attachments to the ultrasonic machines they sell.  A friend and I both ordered Ultrasonic machines from them.   Both the large and small probes on her machine quit working within a month.  They would not replace them.  She finally had to go through her credit card company to deal with the problem.  The large probe on my machine quit working after four months.  Be sure to check that your vendors have warranties on costly equipment purchases.