HEADSET TYPE: Threadless Zero Stack Cup
STEERER TUBE: Tapered 11/8" to 1.5"
MATERIAL: Alloy
STACK HEIGHT: 12.8mm
UPPER CUP: 44mm Flush Cup
LOWER CUP: 56mm Flush Cup
UPPER BEARING: 36° x 45° 11/8" ACB Stainless Steel Sealed Bearing 41.0mm OD
LOWER BEARING: 36° x 45° 1.5" ACB Stainless Steel Sealed Bearing 51.8mm OD

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

Both the upper and lower bearings in this headset are premium stainless steel sealed cartridge units - invest in this upgrade for increased longevity and reliability. 

For tapered steerers (can be converted to 1 1/8 steerer through purchase of a FS160-5538 crown race)