An F1 is a first generation, which is a purebred crossed with another purebred. An F1B is a designer breed crossed back to a Poodle.
For example:
F1- Cavalier X Poodle
F1B- Cavapoo X Poodle
An F1 is a first generation, which is a purebred crossed with another purebred. An F1B is a designer breed crossed back to a Poodle.
For example:
F1- Cavalier X Poodle
F1B- Cavapoo X Poodle

Founded in 1884, the not-for-profit AKC is the recognized and trusted expert in breed, health, and training information for all dogs. AKC actively advocates for responsible dog ownership and is dedicated to advancing dog sports.
Source: akc.org