I have had this adaptor for a while and its really useful for using my 3 16gb Sandisk Extreme cards in my Canon 7D and works well. However i bought this adaptor to use with my Eyefi Pro x2 8gb card and well despite trying several things it does not work. I am a bit annoyed but it is a good adaptor if you dont want to use a wifi card. If you do apparently this adaptor Komputerbay SD to CF Type II High Speed Adapter
has been tested as working with the eyefi Pro cards.
I cant say for sure as i dont have the non pro version but i have read that this adaptor (the Delkin Devices one) works with the non pro (red and blue) Eyefi cards like this Eye-Fi Explore
or Eye-Fi Connect
but i cant confirm this as i have not tested them myself.