Most TENS units aren't typically made for cervical muscles. For their unit, I would apply them at the base I guess, across your shoulders. You don't put the pads directly on the stuff muscles, rather on either side of them. The "current" travels between the pads and across the muscle. You will get much better effect that way.
If they have the really small pads, like size of a quarter, you could do your neck but there is very precise placement of those so you don't do something bad to lymph nodes and other sensitive tissue. I wouldn't advise you to do that.
My TENS was $$$$ and I was glad the insurance paid for it. I was thinking and I believe it was covered 100% at the time because I had already paid my full deductible in from the surgery to remove a few more screws from my leg. By the time the TENS bill came in, my out of pocket was taken care of for the year. It still costs me $20 every few months for pads when I need them. That seemed to be covered the same. Well worth every penny.
