The MEGA brushed ESC jumper is the brains behind adjusting the MEGA speed controller. This item is used to program the features of the NiMh battery mode or the LiPo battery mode (Low Voltage cutoff enabling). You can also adjust whether or not to enable the reverse function with this part. The MEGA brushed ESC jumper are supplied, as standard, on all MEGA brushed speed controllers (two pieces). This pack of four units contains direct replacements in case you lose either of the kit-supplied units.