Not the biggest I've seen by a long way (Magpie once coughed up a whopper) but Mosi coughed up a furball about 3 inches long yesterday. About half an inch diameter. No wonder he wasn't a happy bunny with that inside him. He's bouncing around full of beans now that he's got rid of it. Tbh, Mosi doesn't bring many up. He usually just coughs and I give him extra furball treats. I think they must just pass out the other end. I knew he had a big one this time as he had the runs a bit and that is unlike Mosi. I'm glad he's got it up now but it was the biggest one I've seen him bring up.