The portable water bottle carrier is made of a carabiner and eco-friendly silicone. The outer diameter of the bottle mouth is about 1.38 inches, and the inner diameter is about 1.06 inches. It's a small helper in your life. It can hold water bottles, towels, scarves, storage bags, etc. Suitable for outdoor, climbing, travel, hunting, cycling, fishing, drifting, adventure, hiking, vacation, etc.