A print liquid supply apparatus to be connected to a print system, comprising a container to hold print liquid, having a first, second and third dimension that are perpendicular to each other, and an interface structure to fluidically connect the container to a receiving station of the print system, the interface structure having a first, second and third dimension parallel to said first, second and third dimension of the container, respectively, the interface structure projecting outwards with respect to the container in the direction of the respective first dimensions (D1,d1), and the first dimension of the interface structure being less than half of the first dimension of the container, wherein the interface structure comprises a liquid interface having a seal to fluidically connect to a liquid needle of the receiving station, a liquid channel fluidically connecting the container and the liquid interface, the liquid channel and interface defining a needle insertion direction approximately parallel to the second dimension of the interface, wherein the liquid channel has a needle receiving portion along which the needle is to be inserted into the liquid channel, and a key pen (165, 265, 365, 665D, 665E, 665F, 665G, 965) which extends next to the needle receiving portion of the liquid channel, so that a longitudinal axis along which the key pen extends is approximately parallel to a central axis of the needle receiving portion, the interface structure further comprising a recess housing an integrated circuit contact pad array for connection to a data connector of the print system, wherein contact surfaces of the pads extend in a second virtual reference plane parallel to the second and third dimensions of the interface structure, the contact pad array extending along a line parallel to the third dimension of the interface structure, the contact surfaces of the contact pads facing the container, the second virtual reference plane extending at a distance from a first virtual reference plane parallel to the second and third interface dimensions, the first virtual reference plane intersecting said liquid channel and liquid interface, so that on connection with the print system, the data connector extends into the recess and between the contact surfaces of the contact pad array and the container. the interface structure having a first, second and third dimension parallel to said first, second and third dimension of the container, respectively, the interface structure projecting outwards with respect to the container in the direction of the respective first dimensions (D1,d1), and the first dimension of the interface structure being less than half of the first dimension of the container, wherein a liquid interface having a seal to fluidically connect to a liquid needle of the receiving station, a liquid channel fluidically connecting the container and the liquid interface, the liquid channel and interface defining a needle insertion direction approximately parallel to the second dimension of the interface, wherein the liquid channel has a needle receiving portion along which the needle is to be inserted into the liquid channel, and a key pen (165, 265, 365, 665D, 665E, 665F, 665G, 965) which extends next to the needle receiving portion of the liquid channel, so that a longitudinal axis along which the key pen extends is approximately parallel to a central axis of the needle receiving portion, the interface structure further comprising a recess housing an integrated circuit contact pad array for connection to a data connector of the print system, wherein contact surfaces of the pads extend in a second virtual reference plane parallel to the second and third dimensions of the interface structure, the contact pad array extending along a line parallel to the third dimension of the interface structure, the contact surfaces of the contact pads facing the container,