The municipality included the main islands of Tustna, Stabblandet, and Solskjelsøya, as well as many smaller, surrounding islets between the Edøyfjorden and the Vinjefjorden.

On 1 January 1965, the part of Tustna on the island of Ertvågsøy (population: 85) was transferred to neighboring Aure Municipality to the east.

This means the arms have a blue field (background) and the charge is a klippfisk (a split and salted dried fish, usually cod).

The charge has a tincture of Or which means it is commonly colored yellow, but if it is made out of metal, then gold is used.

The design was chosen to symbolize the importance of the klippfisk industry which was pioneered in the Tustna area starting back in the 1690s.

Traditionally the fish was spread out on rock to sun dry which gives the klippfisk its symmetrical shape (as opposed to the stockfish).