nucleo mobile pistoncino teflon ptfe elettrovalvole ode acciaio inox aisi 316 guarnizioni teflon ptfe 21L1K1T25, 21L1K1T30, 21L2K1T25, 21L2K1T30, 21X2KT120, 21X3KT190, 21X4KT250, 21A2KT15, 21A2KT20, 21A2KT25, 21A2KT30, 21A3KT15, 21A3KT20, 21A3KT25, 21A3KT30,