Tone cap mod for volume knob on guitar

Tone cap mod for volume knob on guitar:
What is this exactly and where can I get it online?
Is it easy to install? just capacitor? Any diagrams anywhere that show the specs and/or installation?

retain highs as the volume control is turned down. One of the three lugs is tied to ground - the cap goes across the other two.

capacitor, some use a capacitor and resistor, etc. But I found the discussion of this type of mod on the Kinman website most interesting.
They explain that you lose highs due to cable capacitance. So instead of just blindly using a .001 mfd capacitor, they recommend using a capacitor that matches your cable capacitance. With their mod, they also use a resistor and they tell you how to figure out what resistor to use. Look at questions 23 and 24 for more details.
I also read about other solutions to the problem of losing highs when turning down the volume. I think one was to use some kind of preamp pedal (I think I saw that on some webpage for Tuck and Patty). I also think using a wireless takes care of the problem somewhat. I think controlling your volume with a volume pedal would work too since they probably have circuitry to prevent the loss of highs.