The Radsail Kite Killer boasts high quality and tip top safety. Unlike some kite killers, the attached cord is elasticated, meaning that they remain effective when used in very strong wind.
I've personally experience a different set of kite killers who's attached cord was not elasticated. When I needed to let go of my kite in strong wind, both cords snapped, leaving just the velcro strap around my wrists, while my kite blew away. - Mat (online-kites.co.uk)
The Radsail kite killer pack includes a kite killer for both your left and right hand.