Shopping Hammock Bliss Sleep Sack - Sleeping I bought these for quick stopovers not wanting to mess up beds. They are too hot. Roomy and comfortable but don't breathe.
Consider ferret comfort over color. Ferrets have limited color vision (they see only some reds), so they really won't care how you choose to decorate their cage. Still, there are a variety of fabrics, patterns, materials, and colors on the market, so you'll have lots of choices to suit your personal tastes. Select hammocks and sleep sacks that are safe and soft, and then see what colors you can get.
Shopping Hammock Bliss Sleep Sack - Sleeping benefit : Comfortable, but not nearly long enough for me at 6'. It barely covers my shoulders and could be a little roomier and I'm a pretty average 180lbs. If they offered other sizes it would be great.
My ferrets prefer lined (or double-layered) hammocks and sleep sacks to unlined ones, perhaps because they are more cozy. And even in Florida, where it is quite warm, my ferrets prefer fleece lining to summer fabrics. I'm guessing that the fleece provides more cushioning and allows for air circulation.