I have an 11 yr old Rag Doll cat who’s been an indoor cat and very nervous. She’s recently had a spell at the vet with acute pancreatitis. I bought this thinking it would help her convalesce. I don’t walk her on this - yet, she’s too nervous, but we’re getting confident being carried out and sat on the grass. This lead means she can explore a little and can’t run off. It needs to be fairly snug otherwise she can easily slip out. She was about 3kg although lost weight due to illness, and I bought the medium size. Fits ok.