The Flex Capacitor!  
 
For techs, luthiers, guitar builders or just the weekend tinker'er.  Got a guitar with cheap, thin or shrill pickups?  Want to beef up your Strat/Tele bridge pickup or toughen up a wimpy humbucker?  Adding a capacitor at the pickup will tame the shrill and add bass and midrange.  But which one do you need to get the sound your looking for?  Flex Capacitor will let you dial in the tone you want.  No guessing or spending hundreds on new pickups hoping to get the right sound!
 
What It Does
Uses a 6 position rotary switch with different values of Capacitors that alters your pickup's tone.  On/Off switch to quickly compare each setting to the original pickup tone. The different capacitor values will cut different amounts of high frequencies, warming up tone and cutting out those ear piercing highs.  Also helps to quiet pickup hiss and other high frequency noise.  Passive power, no battery needed.  Capacitor values for each setting are conveniently noted on the back of the unit. 
 
How To Use
Simply plug your guitar cable into the Flex Capacitor and then another cable out to amplifier.
Turn the seector switch to find a setting that gives you the tone you are looking for and note that capacitor's value.
Install that capacitor value at the hot wire of the pickup.  One leg of the cap at the end of the hot wire (switch or pot) and the other leg to ground. See picture for an example.
  
Capacitors for installation at pickup are not included, but are available online for next to nothing.  Values noted are in Nanofarads.  Google Nanofarad conversion charts for value converters
 
Note: Flex Capacitor can be used in a pedal chain but needs to be 1st in line since there is no battery or pedal power.
 
For techs and guitar shops, this is a budget friendly way to offer pickup upgrades without the cost of new pickups.  Unit pays for itself with one or 2 jobs!