I have never used Transcend CF cards before. In fact, the only CF cards I've ever used are SanDisk and Lexar professional cards. I took a chance on the new 600x Transcend CF cards. Never, Never, Never again! On a recent trip to the Arctic Ocean to photograph polar bears and walruses, I experienced the first CF card failure in more than a decade of digital photography. One of the Transcend 16GB cards I purchased directly from Transcend (Order No. 100046945; SN 305914 0189 8330AB OU6RF), failed miserably. It recorded the first dozen images then gave me nothing but blank images on the last 50 images on the card. It cost me priceless photographs of walruses as they came from the water straight toward me on the beach. I was using a Nikon D300s and 200-400mm f/4 lens. DO NOT USE A TRANSCEND CF CARD UNLESS YOU CAN AFFORD TO LOSE YOUR PHOTOS!