The device for containing fluid substance to be dispensed by manually operated pump, for associating with a rigid container neck, includes a bag having body and neck from which connection flange extends transversally, and a ring cap including bag first connector having an annular connection body, presenting a longitudinal symmetry axis. The annular connection body has a lower portion having a diameter smaller than the bag flange external diameter, and bigger than or equal to the bag neck external diameter; and an upper portion having an annular seat open on the top, having a rest surface lying horizontally for the connection flange.The connection body includes a substantially cylindrical wall and a guide element to guide at least a portion of the flange from a lower free edge of the connection body to the annular seat and prevent the flange (4) from slipping out of the annular seat.