The Silva SOFT FLASK 250ml and 500ml soft bottles are specifically designed for Strive running vests and backpacks, with pockets on the shoulder straps adapted to their shape. The updated design is distinguished by a wide opening, a self-sealing nozzle and an ergonomic shape. The Silva Soft Flask are made of a soft and lightweight TPU material in a light gray shade that is transparent. no BPA, phthalates or PVC The 42mm diameter cap is easy to fill and wash.