Cords get in the way. Gas is a hassle to use, clean up, and store.  Cordless convenience means you don't have to worry about any of that. 

For use with all Black & Decker 18V outdoor power tools.

Compatible with models NST2018, NST1810, NHT518, NS118, NPP2018, and NPT3118.

Simply push down the tab on the back of the battery,  and slide out of unit.  Easy to move from one 18V outdoor Black & Decker tool to the next.