The Bower 500mm f/6.3 Manual Focus Lens is a catadioptric mirror T-mount lens, delivered in this configuration with a T-mount for the Pentax screw mount (aka "M42") system cameras.  This lens is precision manufactured in South Korea.

When combined with the T-mount, this mirror lens mounts to any M42/Pentax screw 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.

This lens has a broad diameter and stocky build, making it a bit easier to handle than a normal refractor lens.  It also has a much different rendering of out of focus areas than a normal lens; highlights will be doughnut-shaped rings with more saturation and contrast on the edge of the ring than on the center.

This lens is an ideal candidate for astrophotography use when mounted to a Vixen GP2 Photo Guider (or other motorized equatorial telescope mount).

Fixed-aperture 500mm f/6.3 mirror lens in T-mount

Multicoated optics

Distinct out-of-focus highlight characterization

White lens barrel helps prevent heat retention

Accepts inexpensive 34mm filters (upon the rear of the lens)

Made in South Korea