22x27mm (4g) or 0.86x1.06in (0.141oz), recommended for all cats and dogs up to 10kg/20lb
25x30mm (7g) or 0.98x1.18in (0.247oz), recommended for dogs 10-25kg/20-50lb
30x35mm (9g) or 1.18x1.38in (0.317oz), recommended for dogs over 25kg/50lb