I don't know exactly, it's gotta be a big enough cavity to decrease weight, but not too big that it makes it weak. I never saw any kind of a cross-cut of one, I just read about it.

 

Being hollow is probably a good reason why some people have said they've never broke one, but have bent some. Personally, I'd rather bend one than break one. At least it won't make you crash. But I don't think I'd go for that warranty. Don't know what the other warranties are, but I'd want them to replace bad axles if the keep bending, which seems pretty likely considering they're hollow. I,too, have never purchased an aftermarket axle but would definetely do my homework if I was going to.

 

Hollow, as in has a hole through it like a pipe... Meaning you could feasilbly look into one end of it and see out the other... That was my thinking when I made that comment.

Well hollow or transparent or solid I'm still very happy with mine and my next bike will have another.

 

hes right, they are hollow