An immature, basic Hollow. They are quite stupid, unable to strategize and only fight using instinct. Easy to fall in traps for that reason or fail to analyze techniques. Each one's power isn't great, but in groups, they could be quite a formidable enemy and not many could defeat a group unharmed.
A more evolved type of Hollow. These Hollows can be quite intelligent sometimes. They can form battle tactics, analyze techniques and be quite battle-smart. They are stronger than basic Hollows as well and can use Cero and Sonido.
Those Hollows usually travel in packs and are very strong, even individually. While slow, they boast Ceros of great destructive energy and very hard skin. They haven't been shown to be intelligent though. It's advised to not face them alone.