Promaster TeleConverter

Does anybody know anything about these? Good or bad how is the quality? Here is the info

PROMASTER 1.7X TELE CANON EOS


The Promaster TeleConverter is designed to be best for use with longer telephoto lenses. When using with over 100mm lenses, it improves the resolution at the peripheral corners and prevents deterioration of light.

* Magnification: 1.7X
* Optical Construction: 4 Elements in 4 Groups
* Coating: Multi-coating
* Max. aperture of lens to ensure AF Operation: F 4.5 or faster
* Exposure magnification: 2 Times
* Depth of filed: One half of prime lens
* Barrel length: 22.5 mm
* Weight: 195 grams
* Max. barrel diameter: 68.5 mm

Bad.

Stay with Canon teleconverters. It's hard enough for them to maintain image quality with there lenses, let alone any third party...particularly when you're shooting with a high res camera like the 5D.

Thanks, I kind of figured by the price.