First all silicone straw cup that holds its shape! GoSili cups are 100% European grade silicone with an embedded stainless steel ring to hold its shape. It won't collapse when gripped. GoSili's patented technology paves the way for a new drinking experience and is the perfect alternative to plastic to-go cups. Dishwasher and microwave safe.easy to use, easy to clean, easy to GoSili. Microwave safe. Dishwasher safe.