If you are a professional photographer or a well seasoned amateur, then you more than likely will not need this card. I am neither and I find it comes in handy quite often, ISince it is plastic laminated I can carry in my camera bag and get it out in any kind of weather. I already had the D-80 camera and "cheat sheet" thus when I got my D-90 I just naturally purchased the same sheet. There are actually 12 sections that covers very briefly the operation of the D-90. This includes a Custom Setting section, Flash photography,white balance,exposure,metering, bracketing,Control panel and Playback. Even if you only seldom use this guide you will find the cost to be minimal for the information listed. By the way, all of the info on the card is also contained in your user manual, however why carry that manual with you everywhere you go? This is well worth the small price paid.