Most things should have a familiar shape, color, pattern, material or some other property, otherwise they will no longer be comfortable. The spoon should have a handle, the floor should be non-slip and easy to clean, and so on. Designers have to follow these frameworks, sometimes deviate from them for the sake of art, and lovers of beautiful things sacrifice convenience. But there are things that can be pretty much anything. And this is where designers have a place to roam.
Let's say hot coasters. Flat and heat resistant - seems to be all that is required of them. Therefore, anything is used, from cloth to CDs. And in such a variety to use some inconspicuous banal stands is just blasphemy.
In this case, we are offered coasters made of felted wool with mathematical signs. Simple, but catchy, and will serve as a wonderful gift for a friend of a mathematician who knows how to cook. And since there are many color schemes, you can choose an option for any kitchen.