This is the class 10 standard and the Transcend Advertising (20 MB / s Read, 10MB / s write) is not reached.
Since I first could not believe that, I have carried out the test in different PCs with built-in card readers and external card readers (Sandisk Micro Mate and Digisol USB2.0 Hi-Speed Multi Card Reader). There was always the same result.
My "only" Class 6 SanDisk Extreme III 4GB SDHC card, however, 20MB Edition revealed
Writing: 14.8 MB / s
Read: 18.0 MB / s
The better reviews here are well justified with an enormous quality scattering (and missing final) in the serial production of Transcend.
Conclusion:
For me, this memory card is not recommended for the storage of HD video and fast sequential shots, eg of digital cameras, camcorders. The relatively low market price sort the card correctly in the Class 6 rez.
May this review have been helpful to you.