Vitakraft Purrk Playfuls Toys for Cats - 4 Mice and 20 Silvervine Refills Total 4 Mice and 20 Silvervine Refills Total Each Package Contains 1 Mouse and 5 Silvervine Refills (4 Packages Included) 100% Natural Powder Derived From Silver vine,Natural Catnip Alternative Purr! Playful Are Stimulating Cat Toys Which Are Infused With Silver vine. Silver vine, A Non-Toxic Plant Grown In East Asia, Has Long Been Known To Elicit Euphoric Responses In Cats! The Reaction To Silver vine Is Similar To The Catnip Response Unlike catnip, cats often return for more Silvervine repeatedly after the effects begin to wear off.