Several Jump-N-Carry jump starter models feature a built-in charger, with the charging tines exiting the case to accept an extension cord connection. This extension cord is properly mated to fit the charger cavity, making it an ideal extension cord to use with your Jump-N-Carry if you don't already have one.
For use with the following JNC jump packs:
JNC4000JNC660JNCAIRJNC770RJNCXF