this series has 66 differents type make up from 13kinds of dia,9 kinds of speed valve,8kinds of install opinion both the top andrear ofthe cylindhave the exhaust valves(exhaust theair),check valve (quick start), and thebuffer valves(adjust the speed of buffer),with chromeplating,the piston rod feautre dustproof,rust proof corrsion proof and wear fesistant, for cylinder dia at rang?40~?200mm,connected with ,UNF,for cyinder dia at rand?220~?320mm connected with flange.