Too many people in the comments refer to quality problems or malfunctions without knowing that they may have had a microSD card whose capacity has been tampered with! An apparent capacity on the packaging and confirmed by the PC but in reality a lower actual capacity.
The use of single H2testw allows to know. After 2 purchases trafficked cards, I am fully satisfied with this purchase Amazon! 12.2 MB / s write and 19,5MO / s read.