Mbran Filtra Introduces the Smallest Portable Water filter in the World Thumb-like portable filter is an industry-leading product and the smallest filter in the world that is unique in its ability to block out bacteria and microplastics. The water flow rate of the the PES hollow fiber membrane portable filter is 3 times faster than its competitors. Due to our portable and electricity-free design, users can get clean, drinkable water anywhere and anytime. Characteristics: 1. electricity-free; 2. block out bacteria and microplastics; 3. high flow rate; 4. 0.2 µm MF-PES hollow fiber membrane.