Omega "Thin" Supplementary Condenser for B-8

These are intended to be used with an Omega B-8 and a 75 mm lens, for 6 X 6 negatives. I know from personal experience that they also work fine with a 60 mm WA lens, for larger prints, which is why I wanted one. According to the late Harry Taylor's website they aren't needed with an 80 mm lens. They're quite difficult to find–much harder than the "thick" supplementary condensers needed for 35mm negatives, with a 50 mm lens (or used to be–Harry had the "thick" condensers made and sold them). I had a standing eBay search for one for over a year before getting one a few years ago; it looks like I never cancelled that search because I got an alert today for this:

http://www.ebay.com/itm/192306517632?ul_noapp=true

I have no knowledge whatsoever about the seller, so, as always, caveat emptor.

Are these necessary for enlarging 6x6 with this enlarger?

Probably NOT necessary. The late Harry Taylor wrote on his website that they're needed for a 75mm lens, but not for an 80. To be honest I'm not even sure if they're necessary for a 60 mm wide angle lens, but I use one and, FWIW, they don't come up for sale that often.