My Archie is 9 months now and 3.5 pounds.
He hasn't grown a bit for a couple of months now -- though I've been praying, for his sake, that he gets a little bigger. I also find it hard to buy clothes for him (coats, sweaters), because he is longish, but so petite. The XS is too short but fits great through the chest, the small is too long and too roomy! He was not sold as a "teacup," he was just the runt of a regular-sized litter.