This Bower 500mm f/6.3 Manual Focus Lens is a catadioptric mirror T-mount lens, delivered with an adapter for Pentax K-mount system cameras.

When combined with the adapter, this mirror lens can be mounted to a Pentax K-mount series camera. However, the fixed f/6.3 aperture is not communicated to the camera body. As such, you can use the lens in "M" manual exposure mode only.