These 120 Ohm resistors are intended to be used with your CAN Bus systems as terminating resistors. Proper CAN buses, such as vehicle or industrial buses, have 120 Ohm termination resistors at the two ends of the bus harnesses.
CTR Electronics products that come with built in terminating resistors (and as such only one additional termination is needed):
PDP (selectable termination via jumper)
Hero (termination by surface mount resistor)
CANivore (selectable termination via software control)
