The set includes all six manned Mercury missions, the Mercury Program Emblem, and the NASA Vector emblem, a total of eight pins.

These pins are made by AB Emblems the NASA Contractor for Mission Emblems. View larger image ...

Each pin is approximately 1 inch in diameter.

Look for the embossing on the back of each pin which reads:

Mercury [mission number]
NASA
ABEmblem.com

to make sure you are getting the authentic AB Emblems pins.