6-Way Capacitor Selector Add-On Kit. Includes a PCB and PCB-Mount switch that will fit in a 9/32 (potentiometer size) hole in an enclosure. The PCB is 2.8cm x 2.1cm. It's a great additional modification for input caps or tone control caps. Many other uses and resistors could be used if you have that need. Comes with or without a set of capacitors.
Here are instructions for using this kit