I just had a look at the gauge in my compressor airline and your correct Cam, it tops out at 220psi. Most pop-off valves on Compressors I have used are set at 120psi, the air tools work in that range. And who other than Racing Pushbikes goes even close to 100psi. Why make a gauge that goes to 220 psi on a machine that never tops 120 with tiny increments around the 20 to 50 range you need a Magnaphying glass to read.