A Fast Ball is a Poké Ball that has a 4x catch rate on Pokémon that have a base speed of 100 or more.
A list of Pokémon that the Fast Ball gives an increased catch rate on can be found here.
Crafting
To craft a Fast Ball, a Fast Ball Lid, a Button, and an Iron Base are required.
To craft a Fast Ball Lid, two red cooked Apricorns and one yellow cooked Apricorn are needed. Placing the 3 cooked Apricorns in a row horizontally in a crafting bench, with the yellow one in the middle, will produce three Fast Ball Disc, and then using the discs on the anvil will make it into Fast Ball Lids.