Feather Pecking - Bit or Bumper

Having tried anti-pecking spray, ensuring lots of space and free ranging, hanging veg/greens and making jackets to protect feather pecked victim, I'm now thinking of something for the beak of the perpetrator. 

The jacket worked a treat, and Bernadette's feathers have grown back, but as soon as I  removed it, Alice was back at it. So she's getting a fixture, but after a bit of googling I'm getting mixed reviews about bits and bumpers.

Which one is best for a lovely Australorp with a really nasty habit?

Thanks

Christine

Bit it is then  Thanks Joyful, I was getting in a pickle reading about which one to get and someone mentioned they where for chicks  :blink:

Poor Alice, but I have no choice and I'd never cull her for bad habits, she's too lovely. 

Apart from the feather pecking that is.