Approximately 6 months of age. Approximately 6-8 pounds.Some kittens at 5 months may need the small size if they are growing fast or are large-breed cats.Small-boned adult cats often wear the small size. If your cat seems smaller than an average full-grown cat, choose small.Each Soft Paws kit contains 40 nail caps, 2 tubes of adhesive, applicator tips and easy to follow instructions. One kit contains enough for 4 front paw applications. Each application lasts approximately 4-6 weeks therefore each kit lasts approximately 4-6 months.