A standard 1-1/8" headset uses two cups that have to be pressed into the frame. These cups are smaller and usually heavier than an internal headset cup. The cups on a standard 1-1/8" headset can serve two purposes. The first purpose is to be the surface that an unsealed bearing rides on and the second is a mating surface for a sealed bearing.
The integrated headset has no cups. An integrated frame actually has the angles needed for the integrated bearing machined into the head tube. The bearing of an integrated headset can be placed directly into the head tube of an integrated frame. Integrated headsets are designed to be easy to install and have a very clean look.
How do I install my headset?
An internal headset uses two aluminum cups that have to be pressed into the frame. These cups are similar to the standard 1-1/8" cups but they a larger in diameter and usually weigh less. The cups on an internal headset provide a mating surface for a sealed cartridge bearing. Once the cups are pressed into the frame, the bearing can be simply placed in its location.