The Avian Standard Integrated carbon headset is generally for pro sized frames that have a 1-1/8" head tube. 

The Avian Step-down Integrated headset is generally for mini-expert sized bikes with a 1-1/8" head tube that uses a fork with a 1" steerer tube. 

• 8mm carbon fiber top cover 
• two 1-1/8" sealed bearings. 
• 1" bearing race & hardware
• 1" star-nut
• Avian laser logo top cap & screw