I will try to explain that one for U all. This only applies to HC (high capicity) cards NOT standard SD cards. Although the same in form factor(size & shape)these cards are rated as Class 2/4/6 This rating is for the writing "SPEED" NOT Maximum Speed BUT Maximim "SUSTAINED" Speed. (or constant speed)
Class 2 = 2mb per Second Class 4 = 4mb per Second Class 6 = 6mb per Second
This card will work in SOME phones and Cameras WITHOUT any converter(Adapter) You should ALWAYS check your manual & familiarize yourself with the proper Form Factor (size & shape) for each device you own as they are all different. Also they are different in the MAXIMUM GB SIZE that they will handle. You may have one Camera that will Support only 1GB and another Camera that supports 32GB. READ YOUR MANUAL AND KNOW YOUR PATICULAR DEVICES PATICULARS Chuck