Asahi Optical Extension Tube + Original Case

This is an extension tube for the M42 mount.
Length: 28.5mm (measured with calipers)
Comes with a case. It might be a bit rare as it's the original case.
Allows for close-up photography with M42 mount lenses. This extension tube is convenient when using M42 lenses with a mount adapter on a digital camera. Since the length is substantial, it would be easier to use with longer focal length lenses.
Asahi Optical is PENTAX, and the logo on the case is an older type.
Please consider it.