We look at generalisations of sets of vectors proving the KochenSpecker theorem in 3 and 4 dimensions. It has been shown that two such sets, although unitarily inequivalent, are part of a larger 3-parameter family of vectors that share the same orthogonality graph. We find that these sets are unusual, in that the vectors in all other Kochen-Specker sets investigated here are fully determined by orthogonality conditions and thus admit no free parameters.The Kochen-Specker (KS) theorem [1] is a statement about the fundamental nature of quantum mechanics: no non-contextual hidden variable theory can reliably reproduce quantum mechanical predictions. The KS theorem states that in a Hilbert space with dimension n ≥ 3 it is impossible to assign definite values v ∈ {0, 1} to m projection operators P m so that for every commuting set of projection operators satisfying P m = I, the corresponding definite values obey v (P m ) = 1. The KS theorem is often visualised by means of a set of "uncolourable" vectors, where projection operators are represented by their constituent rays in Hilbert space and rays can be simplified to vectors as only directions are relevant here. The vectors are coloured according to their pre-assigned values and the summation conditions above translate into colouring rules. This allows us to construct orthogonality graphs that, when uncolourable, provide a contradiction within non-contextual hidden variable models and thus a proof of the KS theorem.Sets of vectors exemplifying the KS theorem have been discovered by numerous authors, with an aim to reduce the number of vectors required to reach a contradiction. Most notably, in a 3-dimensional Hilbert space, the original KS proof of 117 vectors has been replicated with sets using between 31 and 33 vectors [2,3,4,5] and in a 4-dimensional Hilbert space, sets of between 24 and the lower limit of 18 vectors have been realised [2,6,7]. Additionally, an extensive computer search has recently revealed over one thousand of such KS sets in R 4 [8].In a publication by E. Gould and P. K. Aravind [10], two of these sets in 3 dimensions have been shown to share the same orthogonality graph. Specifically, the sets of 33 vectors found by Penrose [3] and Peres [2] have