S-506 is now a 160lb gauge based on information from Milton website. This pump sensor was bought as a gift for my son. It's basically a copy of the one I've had in my garage for about 30 years, except the dial was on the new 160 instead of 120 like my original. I prefer the 120lb scale as it is easier to calibrate and easier to read, but at the moment I need glasses for both scales so it doesn't matter. It is a very handy and very durable tool; In my opinion, it is much more convenient than a standard cartridge and a separate caliber. As mentioned, the one I have is around 30 years old and although it has a lot of wear in places it still works perfectly. I read some of the reviews before buying as there were some negative ones and some people (very very few) complained about the inaccuracy compared to the digital meter. My experience has also been that the gauge can "off" by a pound. or two over the years, but they're easy to calibrate by removing the end cap. A screwdriver and a reference meter (such as a digital or analog meter that you fully trust) is all you need. Remove the end cap where the tubing goes through the loop in the meter body. Then remove the inner hard plastic washer and rubber gasket and slide the gauge cartridge out of the gauge body. Taking into account the inner window of the gauge, loosen the brass screw at the end of the gauge so as not to bend the small red line. cartridge and turn the slotted adjustment screw clockwise if the gauge reads "high" or counterclockwise if it's slightly lower. (All you're doing is adding or decreasing tension on the spring that controls the dial on the gauge.) The adjustment screw is pretty delicate, so don't get carried away. A quarter turn changes the reading on my 120 pound gauge by about 2 pounds. You may have to repeat the setup a few times to get the perfect result, but it really only takes a few minutes. I think I've recalibrated mine about every ten years (only recently when it lost about 2 pounds) and it never went down more than a few pounds at 35psi. If your tires are regularly inflated to a pound or two of the factory recommendation, you're probably more accurate than 90% of the other cars on the road. Gauge Calibration End Point - CHECK that the cartridge scale is aligned and visible on the external gauge. assembly window. All you have to do is twist it right before replacing the end cap and plastic washer in the gauge body. I hope the sizing recommendation is helpful if you are concerned about accuracy or have an old Milton gauge that is losing weight. The gauge itself is a simple, durable commercial design that will last a VERY LONG TIME when you use it at home.