It is very important for every runner to choose the right size of bottle for a longer run. The Compressport ERGOFLASK 300 ML bottle is ideal for a Free Belt thanks to its size. A wide opening for quick and easy refills at the refreshment station. The elastic material shrinks when you drink, so it takes up less space. The valve has a high flow rate.. It fits your hand perfectly, and it is 100 % PVC & BPA-free. It is machine washable.