Dataholic.de:

»With an output of 21 watts, the solar panel of the Solar Charger 21W offers an impressive charging speed, especially under favorable weather conditions with sufficient sunlight. This makes it a reliable source of energy on the go, especially during outdoor activities such as hiking, camping or traveling. The solar panel of the Solar Charger 21W 2xUSB Type-A from Sandberg is not only powerful, but also robust and weatherproof. Its rough textile surface provides excellent grip and durability, which is particularly important when used outdoors. This finish also makes the panel water-repellent, meaning it will not be immediately damaged in the event of rain or snow and will continue to work effectively.«

»The Sandberg Solar Charger 21 W continues to charge even when the sky is overcast, which speaks for the quality of the solar cells used. The ANKER, on the other hand, only works really well in full sunshine and a clear sky.«