To indicate on technical drawings that a shell surface must lie between two coaxial cylinders, the symbol of the cylindrical shape is indicated.
No reference point is described but only the radial distance between two coaxial cylinders, which are placed around the toleranced shell surface.
Cylindricity is a form tolerance.

Cylindricity in Injection Molding

Quality Assurance: Tolerated shell surface with a distance of the imaginary cylinders of 0.06mm

Related topics:

This glossary of plastic industry is provided by PLEXPERT Canada Inc.