Does anyone know what RMY and other auction houses ship them in when you win? Are they these ones that have been mentioned in previous posts?

They ship in polyethylene pages from office depot/staples. OK for the purpose but not what you want to store in for your collection.

I noticed that Ultra Pro now has 8 x 10 and 8.5 x 11 mylar sleeves. There are some for sale on eBay.

I saw that, Adam. The price of the Ultra Pros is pretty good....about $51 for 100 as opposed to $36 for 50 for the Mylite 4s I was about to order.

Actually, I have found the whole PE vs mylar debate rather confusing...there are those 'experts' who swear that mylar should only be used for museum-type conditions where humidity, etc., is well-controlled since it does not 'breathe' as much as PE. Others advocate mylar, as it is used by LOC. In the end, though, I probably have more of my prized photos in mylar....I would guess it is more stable over time?