Sunpak UV/Polarizer Filter Quality?

[Rhombuss]

Could anyone comment on the quality of the Sunpak UV/Polarizing filters? There's a pretty good deal on Ebay, and I'm thinking of purchasing it if the Sunpak filters are of decent quality. I've mainly been keeping my eye out for HOYA deals, but these fit the bill quite nicely.

The UV/polarizers are grouped as a Twin pack, model: CF-7081-TW

Coming up with a google search, everyone seems to be selling it for around the $20 price range. Is there a reason why they're so cheap? Most 62mm circular polarizing filters alone cost about $30-40.

Thanks in advance!