The product description says 'top food grade silicone' [BPA free and safe food grade material]
The material (for everything included) is a very nice, High quality, Food grade Silicone.
They are FDA approved; BPA free, so you can keep them around your food or you can use them in place of a oven glove when the need is apparent.
The coasters are 4.3 inches which provide extra space in case of leakage or spillage.
They also have a pattern to which keeps your cup from slipping or from sticking to the coaster from condensation.

The double-sided Silicone patterned coasters are suitable for every table top/counter top you put them on. They are also heat resistant and can even be used as mittens to get hot pots/pans off the stove.
I really like this set!
I think that it is a great duo combination and something that you wouldn't think to get if you are having drinks with friends for the night.
I found it extremely easy to use the ice mold and in my whiskey tumblers I only needed to use one ice ball. I like that the coasters don't slide and you have to pick them up to move them because I have had a lot of spilled drinks from coasters sliding as someone tries to put a a drink down.

http://amzn.to/1YzLfAK
FYI; I did receive this product at a discounted rate in exchange for my honest review.