I've had a while now, but hesitate to use it, as I'm uncertain of accuracy. Checking C/h flow/ret temps, I was very unsure from the range of temps I got. And the temps didn't sit well with me. I had no other thermometer to do a comparison, so I'm left non the wiser. But I just had a feeling the results were "Way Out" That's why it's been in my drawer for over a year. While I do things the old school way, by experience and feel. This way has never failed me, but for fault finding purposes on boilers, I would have loved this to be part of my every day kit. Please someone prove me wrong?