This paper starts with an attempt to apply the few principles for determining the size of learning objects (LOs) in the literature to a collection of ten mainly Dutch successful learning object practices. From this attempt, a more elaborate model is developed in which LO size is jointly determined by three factors: (1) surface learning versus deep learning (2) resources versus LOs that are passed through (3) arrangement of meaningful units is done within versus outside the LO. These three factors determine (1) the appropriate size of the LOs, (2) the homogeneity of the collection of LOs, (3) the principles that apply in developing the LOs: either Agreement on pedagogy or the following principle: keep the objects as big as possible, unless its parts will be used separately.