For me a good piece on my iMac 27 "(current generation) with i5 processor and 8 GB of RAM is connected. The performance is great with the cards that I have used (SanDisk Extreme). I have a 16GB CF card, Conversely transferred 4.02 GB consisting of 299 files (video and image) in about 1 minute. has lasted about 2 minutes. For me perfectly adequate. Recommended without reservation.