I first saw this item at Lifehacker. I had heard of doing a similar thing, cooling a drink without adding liquid to it, by freezing small fruit.
Being an artist, my mind of course went to – could I do this with more creative shapes. But reading about alaskantomboy‘s experience I realize that may not be a good idea. Since these are used frozen, anything that makes the shape more delicate could easily fracture and put small pieces of stone in a drink; not a good thing.
Warning!: Avoid dropping them! I dropped them a couple of times and you can either escape with a small chip or they will split in half.