Kite killers are leashes that connect  to the brake lines and allow you to let go of the kite if you get into trouble and dump the power instantly with losing the kite.

These are nice.  The padding in the straps is nice and comfy and the Velcro closure is easy and secure.  The tubular webbing leashed with shock-cord inside keeps the leashes short and out of the way while flying and provide some shock relief when the kite killers are deployed.  Both leashes are the the same color but they are labeled for "Left" and "Right".