Instruct: Classify an Amazon review as either positive or negative.
Query: These bottles are a joke!

The problem with these bottles is the newborn slow flow nipple flows too fast. Milk just squirts out when you turn the bottle over and my daughter chokes and she is covered with milk down her chin and neck. Plus, by the time she is half way finished there are so many bubbles inside she gets very gassy.(we make formula ahead of time to avoid shaking the bottle)They have leaked occasionally around the neck.We switched to the best bottles, which are Dr. Browns. They work great! No bubbles or leaking and easy to clean.