The ETFE solar charger is the most durable chargers out of present similar items on the market because of the used special material which called ETFE.
Here we copy some information which comes from google for the definition and advantage of the ETFE material,
1) ETFE (Ethylene-Tetra-Fluoro-Ethylene) is a high-strength fluorine polymer that is corrosion and stain resistant, non-stick self cleaning, and retains its clarity (and therefore light transmittance) ensuring long service life for solar panels.
2) ETFE is robust and unlikely to degrade from exposure to environmental pollution, harsh chemicals or extreme temperature variations increasing the longevity on solar panels.
We have designed 10w, 12w, 14w, 18w, 21w solar chargers, which all laminated by ETFE films. These solar chargers we think can meet almost all the customer's requirements either in outdoor activities or emergency uses.