A timepiece mechanism cassette including at least one bearing surface for positioning the cassette in a movement, a plate and a bar, at least one of which is rigid, and functional components arranged between or on the plate and the bar. At least two of the functional components are movable relative to each other. The plate and bar form an inseparable single piece component with at least one of the functional components and with at least one elastically deformable connecting element. The plate and bar are movable between a proximate position where they are separated by a minimum distance and a distal position where they are separated by a maximum distance. The plate and bar include a snap fit connection for holding them in the proximate position.