The 2011 Five and Alpine 160 both come equipped with a tapered headtube. All tapered Orange bikes use the Frustum ZS standard with ZeroStack 1-1/8" top and 1.5" bottom. See Cane Creek information here. The top cup is 44mm ZS with 55.9mm ZS lower cup sizing. Cane Creek, Hope and Chris King all produce headsets for this standard. The Hope part number for a compatible system using a tapered steerer fork is HSTN, if you want to run a traditional 1-1/8" fork in a tapered frame, add the step down crown race, part number HS136.