One set for each of my thee race engines; the 906, 2.8 and 3.0 RSR.These are exact reproductions of the 906/911 RSR camshaft Aluminum Racing Gears. The gears were made from an aerospace Aluminum material called "ALZNMGCU" (1,5). For reference and you might find interesting, I have also researched some articles that talk about the ALZNMGCU alloy https://pbase.com/slidevalve911rsr/myrsr_30ltr_gears_camshafts_articles_alznmgcu