I bought the wrong ink cartridges for my 3880; they're the ones (T5803 and T5806) that are only useable with the 3800. I didn't notice the error until long after my 30-day return period had expired, so I'm stuck with them.
If you use an Epson 3800, and you live anywhere in the U.S. that USPS will deliver a Priority Mail box, PM me with your name and mailing address, and I'll ship them out to you. If you feel like giving a few extra bucks to your favorite charity, or mine (St. Jude Children's Research Hospital,
www.stjude.org), that would be great.
Happy New Year!
Steve