Variants of a mold are catalogued separately, so each one has its own sets and minifigs. Check these too if something you expect is missing here.

• 71308 Sail, Triangular, 15 x 22 [Plain] this part is a pair of it
• upn0027pr0001 Sail, Square, 25 x 25 with Crossed Cannons Print this part is a pair of it