Designed to fit into a zero stack (44mm ID) head tube, but allow the use of a tapered steer fork. 

• ACB with Forged alloy upper cup
• ACB with Forged alloy lower cup
• Stainless steel crown race
• FSA Part Number 101-1321A

Not sure if this is the one you need?
Check out the handy FSA Headset ID Tool here http://www.fsaeasyheadset.com/