tee-hai-dau-ren-trong-1-dau-ren-ngoai-phay-cnc-bang-dong

ket noi khop noi t 3 dau ren de ket noi voi cac khop noi ren khac co ba dau noi mot noi thang chia ra 2 goc cong 90 do cho noi ong cho he thong