Protein complex that links the outer microtubule doublet of the ciliary or flagellum axoneme with the sheath that surrounds the central pair of microtubules. Composed of a stalk that attaches to each doublet microtubule and a globular structure (spoke head) that projects toward the central pair of microtubules. [ http://www.ncbi.nlm.nih.gov/pubmed/9450971 https://www.worldcat.org/search?q=bn%3A0124325653 ]