Although Arlo commutes with me on the subway in an open tote AND peacefully sleeps enclosed in a crate at night, her willingness to enter a more compact and zipped-up travel bag was limited. The carrier is definitely sized for small (I would say 15-lbs and under, although Wild One suggests 16-lbs) pets, and long-legged Arlo (at 14.5 lbs) was a tight fit. Once I was able to get her to comfortably lie down inside the carrier with a treat, she relaxed and I was able to zip it up. She didn't have room to stand up, but wasn't crammed in there either — she looked snug and cozy in there. I carried her around my apartment in it, shoulder-strap style, without panic (from either of us).