A shim tray (10) for a main magnet system of a magnetic resonance examination system comprises a plurality of shim pockets (11), of which an individual shim pocket has side walls (21, 42) forming an open channel (11). Two opposite lateral side walls (21) have insertion profiles (22) to receive an end shim-element (13) at least one open channel's end. Essentially the entire volume of the channel of the shim pocket is available to hold passive shim elements.