Brake Pad Thickness Gauge.
 

Any opinions or observations please?
I normally check the thickness of the brake pads on my car when I service the brake calipers (remove/clean/lubricate).
However, I rarely have access to my daughter’s XC70 long enough to do that and as it is an automatic the brakes tend to get well used.
I’m considering buying a “brake pad thickness gauge” so that I can do a quick check when I get the chance.
There is one by Laser, (6678) the “hook” of which locates on the inner edge of the brake pad backing plate so providing a measurement of the actual pad thickness.
There is one by Sealey (VS058) the “hook” of which locates on the outer edge of the brake pad backing plate so the measurement includes the thickness of the backing plate hence the thickness of the backing plate must be deducted from the actual measurement to establish the thickness of the actual pad lining. I believe that most, but not all, backing plates are 6.0 mms. thick.
Each of the above cost considerably more than various other gauges which are available, all of which appear to include the backing plate thickness in the displayed measurement, as per the Sealey, but the cheap ones all appear to originate from China and I would prefer to avoid Chinese products if possible.

I also need to know whether the gauge can be used on the inner side of the brake to measure the inner pad although I cannot think of any reason why this may not be possible.

Has anyone bought or used such a gauge and do they do what they purport to do?