Telescope mirror used in the PiKon design. Mirror only.
Focal length 500mm, 4.5” (114mm) diameter, spherical, Aluminium mirror suitable for PiKon and Newtonian reflecting telescope.
Full information on building a PiKon telescope is here:
Instructions and 3D Print Files
PiKon on Instructables.com
PiKon on Thingieverse.com
Make Live build a PiKon (video)