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.

• 3614b Plate Round 1 x 1 with Towball and Hexagonal Hole [Maxifig Hand] Mold of this part
• 3613 Arm Piece with Towball Socket, 3 Fingers Pair of this part