A rack assembly of storage bins has a back wall, series of vertical slots in the back wall, partition members having tongues for fixing the partition member to the back wall. Extending between the partition members are bin floors, the edges of the floor members located in slots in the partition members. The spacing of the slots in the back wall and of the slots in the partition members is selected to permit a range of spacings of horizontally adjacent partition members and a range of spacings of vertically adjacent floor members. By suitable selection of the spacings, a large variety of bin sizes can be obtained.