This small PCB gives the trimmer resistor inside of your mod a more finished look. It fits the popular BI Technologies/ TT Electronics Model 93 1/2 inch thumb wheel potentiometer (http://www.mouser.com/ProductDetail/BI-Technologies-TT-Electronics/93PR200LF/?qs=UjOdgN%2FjCTWH6fryvuD2%2Fg%3D%3D). This style of potentiometer comes in versions rated from 20 ohms to 2 megaohms, but the 200, 1k, 10k and 100k ohm versions are most commonly used for regulation of custom box mods. This mini board is designed for use with DC/DC regulator builds (OKR, OKL, Raptor, Delta, etc.,) that normally call for a 200 ohm potentiometer and that already have a 220 ohm resistor wired in series before it. The PCB can accommodate a 1206 or 1210 SMD package size resistor in parallel between pins 1 and 3 of the the pot for more fine tuned control if the 1k version of model 93 pot is being used.