Autometer made some faulty pyrometers, or slow reading and are not good for the Cummins. I learned the hard way after installing it. It was showing temps way too cool to be true, and extremely slow movement, then I found out that I had the "bullet shaped" probe, aka the bad one. I called autometer and they were good to me and sent a new probe and gauge with everything. Here is a pic I made showing the stepped probe, (the good one) and the Bullet shaped probe (the bad one). I installed the new gauge assembly and it works fine now. It works fast showing an accurate reading. It took a while but I now have my pyrometer!