This Silicone Sleeve fits 4oz and 8oz regular-mouth mason jars. While it was designed for the bottle, it is useful well beyond the baby stage! It provides extra protection and a better grip during use as a bottle, sippy cup or even a snack container. The sleeve has volume markings in ounces & milliliters and windows on both sides allows easy viewing of contents. It is dishwasher-safe. All components are made in the USA.