When purchasing NASA pins, look for the embossing on the back:

Expedition 21
NASA
ABEmblem.com

to make sure you are getting the NASA authorized version of the pin.

Expedition 21 begins with the Soyuz TMA-14 undocking in October 2009. Two new crew members will arrive on Soyuz TMA-16 for the handover before the previous crew departs.

At right: NASA astronaut Nicole Stott, Canadian Space Agency astronaut Robert Thirsk (left), both Expedition 20/21 flight engineers; and European Space Agency astronaut Frank De Winne, Expedition 20 flight engineer and Expedition 21 commander, participate in a training session in the Jake Garn Simulation and Training Facility at NASA's Johnson Space Center. Image credit: NASA