These are the excellent Pentax Auto A Bellows. The engineering allows both front and rear standards to be adjusted which makes it an extremely useful tool for macro photography.
Pentax K mount but adaptors are available for most digital cameras. Recommended for use with the Nikon EL 50mm f2.8 lens in straightforward configuration or reverse mounted for additional magnification.
The bellows show signs of slight crushing but are completely light tight
For additional information see Murray O’Neill’s excellent e-book “The PENTAX Bellows Overlooked..Underused..Elegant” available for free download
Category: Cameras and Photography:Lenses and Filters:Lens Adapters, Mounts and Tubes