For Arduino boards and shields, stacking is extremely important. By stacking Arduino boards and shields can be placed properly and extra work like soldering or wiring is kept at minimum. The new products developed for Arduino platform is generally intented to be stacking-friendly. Shield Stacking Headers for Arduino is an important tool used for that purpose.
The set includes 1x 10-pin header, 2x 8-pin headers, 2x 6-pin headers, and one 2x 3-pin header. The legs are all 10.5mm long, so after PCB thickness (1.7mm) you have a height of 8.8mm - just enough to clear the Arduino's USB-B connector.
Adafruit Web Site