SmartyKat Madcap Mania adorable mice are refillable for nonstop fun and excitement! Includes a 2-gram tube of SmartyKat pure and potent catnip. Refillable catnip toys are by far the best way to allow you to refresh the catnip in your cat’s favorite toy for endless fun. Most cats respond to catnip with a burst of energetic activity followed by a calm mellow period.