You mean Vintage Trailer Supply and Airstream Supply? As I look on the two sites, if I am looking at wing windows for 1970-83 trailers I see a difference of about $20 on a part approaching $300. Doesn't seem like a huge difference to me. You might find that the difference becomes even smaller when the seller adds the shipping to your order. Actually, as I read the small print, I see that Airstream Supply has an additional fee of $12 for a special shipping box, and VTS includes a "complimentary" splice bar, which ought to be worth a few bucks. At the end of the day, it looks like the prices are pretty darn similar.