FSA's core line of headsets that have become an industry benchmark \n Orbit IS, CF, Z, ZS, X, MX, XL II include angular contact bearings \n Orbit Xtreme Pro include stainless steel industrial cartridge bearings and stainless crown race \n Orbit UF include lower angular contact bearing and upper 5/32" caged bearing \n Orbit DL include 5/32" caged bearings \n IS: 36x45 degree Cane Creek Integrated, CF: 45x45 degree Campagnolo Integrated, ZS: ZeroStack shallow, Z: ZeroStack deep, or XtremePro, X, MX, XLII, UF, DL: External Cup traditional available for 1", 11/8", tapered and 1.5" applications \n For clarification go to http://www.fsaeasyheadset.com