Assembly kit for a mixer tap fitted with two separate water attachments (8, 10) connectable to two respective separate water intakes (12, 14), - the kit comprising a first connection bush suitable to be fluidically connected to a water intake (12,14) by means of a shaped coupling, the first connection bush having a housing seat on the side opposite the associable water intake (12,14), the first bush having a first assembly axis (X-X) which defines a centering position of the first bush in relation to the associable water intake (12, 24), - a second connection bush suitable to be fluidically connected to a water attachment (8, 10) of the mixer tap by means of a shaped coupling, - the second connection bush having a connection extremity suitable to engage in the housing seat of the first bush, - the second bush having a second assembly axis (Y-Y) which defines a centering position of the second bush in relation to the associable water attachment (8,10) of the mixer tap, - wherein the connection extremity of the second bush engages in the housing seat of the first bush forming a shaped coupling, - and wherein at least one between the connection extremity and the housing seat has a misalignment in relation to the assembly axis (X-X, Y-Y) of the respective bush (24,40), so that by varying the relative angular position of the first and second bush (24,40), it is possible to misalign the bushes (24,40) with each other, to adapt the position of the respective assembly axes (X-X, Y-Y) to the respective water intakes (12,14) and attachments (8,10) of the mixer tap, characterised in that the connection extremity comprises an attachment hole housing a fastening element which axially blocks the two bushes (24, 40), to each other, wherein during assembly of the kit the fastening element is inserted inside the housing seat and blocks itself mechanically over said attachment hole, wherein said fastening element comprises a through hole to allow the passage of water through the bushes (24, 40). - the kit comprising a first connection bush suitable to be fluidically connected to a water intake (12,14) by means of a shaped coupling, the first connection bush having a housing seat on the side opposite the associable water intake (12,14), the first bush having a first assembly axis (X-X) which defines a centering position of the first bush in relation to the associable water intake (12, 24), - a second connection bush suitable to be fluidically connected to a water attachment (8, 10) of the mixer tap by means of a shaped coupling, - the second connection bush having a connection extremity suitable to engage in the housing seat of the first bush, - the second bush having a second assembly axis (Y-Y) which defines a centering position of the second bush in relation to the associable water attachment (8,10) of the mixer tap, - wherein the connection extremity of the second bush engages in the housing seat of the first bush forming a shaped coupling, - and wherein at least one between the connection extremity and the housing seat has a misalignment in relation to the assembly axis (X-X, Y-Y) of the respective bush (24,40), so that by varying the relative angular position of the first and second bush (24,40), it is possible to misalign the bushes (24,40) with each other, to adapt the position of the respective assembly axes (X-X, Y-Y) to the respective water intakes (12,14) and attachments (8,10) of the mixer tap,