first i live in morocco things that are in usa arent  in my contry hello please i have bought mastery of hand strength by john brookfield and he recommend wire cutting exercice to build crushing grip, he says The best wire to use is regular fence wire that you see around most farms. This size wire has the right strength and thickness to give your grip a workout. please, but i didnt understand which type of wire should i use is it metal wire, and what about the thickness , and it is barbered