Hub/unit bearings are what your front wheel roll on , they bolt to the steering knuckle , the axle is splined which engages an internal spline in the drive flange. 87 and up wranglers use this design , older models had wheel bearings that could be serviced and re-packed . Hub / unit bearings are non-servicable and are throw away's , like a lot of things today , when worn out they are removed and replaced.