Brake lever return spring for 70's style Domino controls. These were commonly found on most Italian made bikes in the 70's. Some had a diamond shaped CEV switch attached to the controls. This fits inside of the brake lever. Its not uncommon for the old rusty originals to break. These are new old stock, oem replacements.
In the 80's most brands swapped over to the black plastic control sets. These are NOT for those. Those have a smaller shorter spring inside. Compare to your original to be sure!