A Heavy Ball is a Poké Ball for catching very heavy Pokémon. It can be obtained by crafting it, buying from a shopkeeper, or as a tier 1 special drop,
Unlike most Poké Balls, the Heavy Ball's catch rate modifier is additive rather than multiplicative. The catch rate modifier for Heavy Balls based on Pokémon weight is as follows:
A list of Pokémon that have an increased catch rate with a Heavy Ball can be found here.
Heavy Balls are crafted similarly to other Poké Balls.