Not stainless steel!
I ordered these bowls a month ago and they have been in use for maybe half of that time. I always wash stainless steel by hand and since my cats are on a dry diet the bowls are easy to clean. Even so, after just this short period of light use, handwashing only and immediate drying, one of the bowls already has rust spots. I have stainless steel bowls that I bought for my cats 12 years ago and they are spotless. I will definitely try to get a refund as there seems to be a fault with the product.