These headers are made to work with the Arduino Uno R3, Leonardo and new Arduino boards going forward. They are the perfect height for clearing the USB-B connector and great for stacking multiple shields. This kit includes four headers (two 8-pin, one 10-pin and one 6-pin) — enough to connect a shield to an Arduino board.
Note: If you have an Uno R2, original Uno, Duemilanove, or Arduino Pro made in 2011 or earlier, this is the wrong header kit for you. You should instead get the PRT-10007 kit.