Aetertek WALL CHARGER WITH USB DUAL CHARGING CABLE DOG TRAINING SYSTEMS,GROOVYPETS MODELS CHARGE TWO UNITS AT THE SAME TIME; DETACHABLE USB CHARGING CALBE W/ 2MM CHARGING PINS TO CHARGE VIA A COMPUTER; WORKS WITH GROOVYPETS MODELS(NOT GP-330 MODEL) AND MOST AETERTEK MODELS(GT-211/AT-211D,AT-215,AT-216,AT-218,AT-219,AT-918,AT-919); WORKS WITH MANY OTHER BRANDS IF CHARGING PORT IS 2MM IN DIAMETER(READ Q&A FOR DETAILS); ******WORKS WITH NEW AT-211D BUT DOES NOT WORK WITH NEWEST AETERTEK C or D MODELS SUCH AS AT-216C/D,AT-918C,AT-919C;