Whetfish Fin+ is a consumable Pouch Item in Monster Hunter World (MHW). These and other Items from fish can be gathered in the field and brought along on hunts.
A fish fin used to sharpen weapons. Works better than a whetstone, and can be reused if you're lucky.
Whetfish Fins+ can be used from the Item Bar while in the field to restore the Sharpness of a Weapon, similarly to a Whetstone. These fins perform even better than common Whetfish Fins, requiring only 1 cycle, and are equivalent to level 3 Speed Sharpening. Whetfish Fins+ have a 10% chance to be consumed upon use.
Note: Multiple sharpening speed effects don't stack, only the strongest individual effect (lowest number of cycles) is used. Speed Sharpening and Felyne Polisher thus have no effect when using a Whetfish Fin+.
How to Acquire Whetfish Fin+
Whetfish Fins+ are obtained by using the Fishing Rod to catch Great Whetfish out in the field. Each successful completion of the fishing mini-game will yield one Fin+. Great Whetfish have a chance to spawn in any area where regular Whetfish can be found. Their eyes have a turquoise glow and seem to occur more frequently during in-game night-time.
The Master Rank Event Quest: "A Fish to Whet Your Appetite" is guaranteed to reward 2 Fins+ with a high chance for more, and can be completed in less than 2 minutes.