Petco is a nationwide retail chain that sells dog, cat, fish, reptile, and small mammal supplies like food, treats, crates, litter boxes, toys, and grooming accessories. Rather than focus on selling one brand, like Purina, it strives to have the best selection of small pet supplies that would convince shoppers that they were the "go-to" for their pets' needs. These stores could best be described as ________. convenience stores category killers specialty stores warehouse clubs