6-point diamonds, or 60 degree diamonds get their name from the star they make. Their size is measured along one side, and all sides are equal. They're versatile and pretty and play so nicely with many other pieces.
Most of the quilts in the photos use 2" Diamonds.
6-point Diamond acrylic templates can be found here.
You will receive the number of paper pieces listed in the options after the size. Listing is for paper pieces only.