Katadyn
Katadyn BeFree 1.0 L
A 0.1-micron hollow-fibre filter in a collapsible flask. Fast flow, field-cleanable by shaking, and light enough that people actually carry it.
L1-WAT-02 asks for a filtration method rated to 0.1 micron or finer that a student can clear in the field without tools. The BeFree meets both and its flow rate is high enough that students keep using it instead of quietly drinking untreated water, which is the real failure mode.
