A shelf for a merchandise display unit, comprising: a base mountable to an upright so as to extend therefrom in a fixed position, the base comprising a bottom wall and parallel side walls upstanding from opposing edges of the bottom wall, each parallel side wall having an elongate slot extending in a direction away from an upright when the base is mounted thereto, a tray including a floor to support merchandise thereon, the tray having parallel side panels upstanding from opposing edges of the floor, and a tongue extending from each side panel in a lateral direction away from each other, wherein the tray is configured to nest within the base with each tongue received in a corresponding one of said elongate slots in the side walls of the base so that the tray is slideable relative to the base away from the upright with each tongue travelling along its corresponding slot, and wherein each side wall of the base has a front edge remote from an upright when the base is mounted thereto, and the elongate slot in each side wall has a front end that stops short of the front edge so that sliding of the tray relative to the base is limited by engagement of each tongue with the front end of the slot in which it travels, and wherein each slot has a section that extends downwardly towards its front end so that the tray tilts downwardly as the tongue travels along said downwardly extending section, and characterised in that each slot has a step adjacent to said section that extends downwardly to its front end, the tongue being caught by said step prior to travelling along said downwardly extending section to restrain the tray in an extended but untilted orientation. a base mountable to an upright so as to extend therefrom in a fixed position, the base comprising a bottom wall and parallel side walls upstanding from opposing edges of the bottom wall, each parallel side wall having an elongate slot extending in a direction away from an upright when the base is mounted thereto, a tray including a floor to support merchandise thereon, the tray having parallel side panels upstanding from opposing edges of the floor, and a tongue extending from each side panel in a lateral direction away from each other, wherein the tray is configured to nest within the base with each tongue received in a corresponding one of said elongate slots in the side walls of the base so that the tray is slideable relative to the base away from the upright with each tongue travelling along its corresponding slot, and wherein each side wall of the base has a front edge remote from an upright when the base is mounted thereto, and the elongate slot in each side wall has a front end that stops short of the front edge so that sliding of the tray relative to the base is limited by engagement of each tongue with the front end of the slot in which it travels, and wherein each slot has a section that extends downwardly towards its front end so that the tray tilts downwardly as the tongue travels along said downwardly extending section, and characterised in that each slot has a step adjacent to said section that extends downwardly to its front end, the tongue being caught by said step prior to travelling along said downwardly extending section to restrain the tray in an extended but untilted orientation.