I was interested in trying this neck wrap as I occasionally get stiffness, sometimes accompanied by a slight ache, in my neck area. I read the literature included in the package carefully, noting the warnings about over-heating in the microwave. This neck wrap can be used hot or cold. For heat, place on turntable of the microwave, spreading it out into the c-shape so the filling is evenly distributed. I heated it for 45 seconds on high, then turned it over for another 45 seconds to make sure it was heated evenly. That was enough time for me, but you can continue heating in 10 second increments if you want it a little warmer. The zipper that allows you to remove the plush cover for washing is made of PVC material so it's microwave safe.
I have worn the wrap, heated as described, while sitting at my computer for 30 to 45 minutes and it stays warm for that length of time. My neck feels much better after wearing it. The ache is gone and most of the stiffness also. It can also be used in cold weather just to help keep you warm and cozy.
Since I am mostly interested in the heat function of this wrap, I haven't tried the cold application.