What serum does Kim Kardashian use?

Could you please clarify what exactly you're asking about in relation to Kim Kardashian and serum? Are you referring to a skincare product or some other type of serum? If it's related to skincare, it's worth noting that Kim Kardashian, like many celebrities, often promotes various skincare products and treatments, but the specific serum she uses might not be widely known or might change over time. It's also important to remember that everyone's skin is unique and responds differently to different products, so what works for Kim Kardashian might not necessarily work for someone else. Can you provide more context or specify the type of serum you're inquiring about?