It fit and worked well. My only concern was that there were not installation instructions. Instructions are on the ZWO web site but there in no information on how to find it included with the Dew Heater. Installation and operation are fairly simple so this is not too much of an issue.
The dew heater works perfectly on my ASI1600mm-Pro. My problems with a dewed up focal plane window are over. My one complaint is that ZWO should have included an integral heater within the body of the camera.
Chris Hendren knows his stuff. The only issue I have is the camera is a USB 3 device and I'm having trouble with my current ICRON HUB which is USB 2.