Apex Legends offers not only a wide variety of cool armaments to murder other players with, but also a wide variety of tools allowing continued survival in the battlefield. The Purple Knockdown Shield is one of the most helpful such tools.
Apex Legends Purple Knockdown Shield is very close to being the best knockdown shield in the game (Epic tier - secondary to Legendary), but the Golden Knockdown Shield doesn't block any more damage than the Purple one does. Find more info below!
Purple Knockdown Shield Health
Purple Knockdown Shield can be found the same way you find all of your loot and items in Apex Legends: by scouring the level and sifting through Supply Drops. This means that you getting one is dependent entirely on RNG, though you could loot one off a dead body, too.
As for Purple Knockdown Shield health; it can block the same amount of damage as the Golden, Legendary Knockdown Shield - 750. However, Purple lacks the 'Resurrection' ability of Golden, which allows you to self-revive once.
This means that, in practice, Purple Knockdown Shield isn't the best shield in the game, but it is up-to-par for the most part. Really, only trade it in for the Golden Knockdown Shield if you find one, otherwise stick with Purple.