Evolution Items

Evolution Items are items necessary to evolve certain species of Pokémon. There are currently seven items that can be obtained in game:
 * Dragon Scale
 * King's Rock
 * Metal Coat
 * Sun Stone
 * Up-Grade
 * Sinnoh Stone
 * Unova Stone

In order to see the evolution items that a player owns, one has to check out the item bag page.

Johto items
All of the Johto items have a small chance of being obtained from spinning Photo Discs in PokéStops and Gyms. Trainers are also guaranteed one from completing a seven day spin streak. They can be also be obtained as rewards from research tasks and gifts.

Sinnoh Stone
Sinnoh Stones can be obtained by claiming Research Breakthrough rewards. These also have a small chance of being rewards for participating in Trainer Battles.

Unova Stone
Sinnoh Stones can be obtained by claiming Research Breakthrough rewards. These also have a small chance of being rewards for defeating Team GO Rocket Leaders.

Trivia

 * The Porygon family is the only evolutionary line that requires two different evolution items to evolve, one for each stage.
 * All Pokémon that result from using these items cannot be caught in the wild, hatched from an egg, be a Raid Boss in a gym, or be a reward obtained from research tasks under normal conditions, and the only way to acquire them is through item evolution.
 * Only exception are Pokémon spawned by using a Daily Adventure Incense.
 * Historically in the core-series of Pokémon games, Pokémon that evolve with a Dragon Scale, a King's Rock, a Metal Coat or an Up-Grade must be traded while doing so, in order to trigger the evolution process.
 * Pokémon that evolve by holding a Sun Stone on the other hand, do not need to be traded to the process is triggered.
 * On the official support page for Pokémon GO, Deepsea Scale and Deepsea Tooth were mentioned.
 * In the main series games, these items are required to evolve Clamperl into either Huntail or Gorebyss respectively.
 * This concept was scrapped. The evolution of Clamperl is finally decided to be random.
 * The Sinnoh Stone was first discovered in network traffic on November, 2018.
 * The design of the Sinnoh Stone suggests that it is composed of diamond and pearl-like materials, which is a reference to the Pokémon: Diamond and Pearl games, in which the Sinnoh region was first introduced.
 * Similar to the Sinnoh Stone, the Unova Stone is composed of black and white materials, which is reference to the Pokémon: Black and White games, in which the Unova region was first introduced.
 * Sinnoh Stones were guaranteed Research Breakthrough rewards during Hatchathon 2018.
 * During the February 2019 Community Day, Trainers were guaranteed to receive up to five Sinnoh Stones as a reward from Trainer Battles; in order to evolve their Piloswine into Mamoswine.
 * No Sinnoh Stone was guaranteed on August 2019 Community Day for evolving Kirlia into Gallade.
 * During the February 2020 Community Day, Trainers were guaranteed to receive two Sinnoh Stones as a reward from one set of GO Battle League completed; in order to evolve their Rhydon into Rhyperior.