Himalayan Dog Chews are made by boiling yak and cow milk and then dried for several weeks to create a hard chew. It's 100% natural with no preservatives. The result is a dog treat that is not too soft and not too hard, while maintaining the same cheesy flavor dogs love! Pieces must be microwaved for 1 minute to 1 minute 30 seconds. Please watch the microwave, as Himalayan puffs are made of cheese and do not pop like normal popcorn.