This is a measure of the amount of work required to return your car to original after removing a previously-installed Precision Matters product. Or, from the other direction, how far from stock your car will become after fitting one of our products.
At one end, after removing our Timing Kit, you would re-install the stock distributor clamp and there would remain no evidence of it ever being fitted. Even if the engine was later disassembled. This example is very near the left (green) end of the scale:
Our most-invasive product to date is the Remote Oil Adapter. It requires (along with our Full Flow Filter Adapter) a notch hidden inside the oil pump cavity, plus some drilling of the car undercarriage to mount the filter bracket (not of our manufacture). It's honest to claim that this is not very invasive, so the pointer is still at about 1/4 of the scale.
If, however, you were to drill your engine case to fit a full-flow filter, our scale would show that as very invasive, so the pointer moves pretty drastically to the right.
Some of our products have a variable index, depending on whether you modify your (removable) parts or substitute spares; see Twin-Plug or 36mm Zeniths.
Nearly all of our products are designed to stay close to the left end of the scale, so that's where you'll find the indicator. But future products may deviate from that norm, so the scale is continued toward the right.
When you 'mouse' over the scale on the Product images, a small window will open offering some specifics, but in general, left (green) is easier to return to original than right (red.)