The invention relates to a lead through for fluid tight connection of a mixer assembly to a roof of a fluid housing digestion tank, comprising a first element (12), which presents a central opening and an axially extending centre axis, and a second element (13), which presents a central opening and an axially extending centre axis, the extension of the centre axis of the second element (13) being adjustable in relation to the extension of the centre axis of the first element (12). According to the invention the lead through comprises a means for making an interface fluid tight located at the interface between the first element (12) and the second element (13), at least three positioning members being arranged to determine the mutual positions of the first element (12) and the second element (13) in the axial direction, at least two of said positioning members being constituted by mutually independent adjustment members (24), which in relation to said fluid housing tank (1) are located on the opposite side of said means for making an interface fluid tight.
