Hyphessobrycon amandae, aka the Fire, Red, Amber, or Amanda's tetra, is a small species of tetra from Brazil. These are among the smallest of tetras and max out around 1" or less. They mix well with small community fishes, but obviously take care not to house them with anything large enough to see them as food.
This is a batch of adult individuals. They are about 0.5-0.75" long.