Large opening for ease of use - Our water bag has a large opening for easy filling. It is wide enough to allow the brush to easily access the inside of the water bag. The 4" screw cap is easy to put on and take off. Add ice cubes directly to get cold water. The inside of the hydration bladder is smooth and easy to clean. Super Quality - The entire hydration bladder is made from high quality materials. The water bladder also passed the pneumatic pressure test. The double-sided heat-sealing technology greatly improves the durability of the water bladder. The bladder is equipped with a high-flow valve. The flexible mouthpiece has an easy to open and close valve. It also has a lid that keeps dirt out. The connector closes automatically when the tube is removed and the bladder remains full.