Here's why:
* Genitals are small: Before this age, the genitals of both male and female rabbits are very small and can be difficult to distinguish.
* Testicles descend: At around this age, male rabbits' testicles start to descend into their scrotum, making them more obvious.
* Vulva: The vulva of a female rabbit becomes more pronounced and easier to identify as well.
However, it's best to have a veterinarian or experienced rabbit breeder confirm the sex of your rabbit. They can accurately identify the sex based on the rabbit's anatomy.