Soldering SMDs is very difficult, but these pre-wired units take all the work out of it! 0603 SMD units are very small and difficult to solder! Each unit comes with pre-soldered micro litz wired leads attached on the back of the unit with both leads laying flat and coming off the SMD in the same direction. Each unit comes with a resistor for 12v operation pre-soldered and wire leads about six to seven inches long.