Replace the stock 256MB card with this.  Works just as described.  For those types of products, brand doesn't really matter.  But you can never go wrong with Kingston.  The actually capacity of the card is 3.6GB, same as all other 4 GB microSDHC card.  As a class 4 card, it is much faster than those cheap SD cards that came with your phone or other gadgets.  For blackberry users who enjoy some music on the go, you will be pleased to find that you can cache around 25 Slacker radio stations on the card.  The card won't transform your phone like what it says in the advertisement, but it is certainly a nice addition to any gadgets depending on your usage.