Directions are for a 5-cup teapot but the pattern is adjustable. According to the directions 13sts in daffodil stitch equals 1/2 inch (keeping in mind that daffodil stitch decreases rapidly over 14 rows) so this cosy should fit a teapot of approximately 12.5 inches circumference.

Gauge over stocking stitch is approximately 26sts to 4 inches (the daffodil stitch is pleated and is drastically decreased over 14 rows so it takes many more stitches per inch).

Pattern is also available from The Western Mail via Trove.