Hardcore headset for extreme riders! For use with tapered zerostack headtube and tapered 1 1/8 inch to 1.5 inch fork steerer.Features:Internal headset for tapered head tube and 1 1/8 to 1.5 inch tapered forkUpper: 36/ 45 degree ACB (Blue seal)Lower: 1.5 inch 36/45 degree ACB (Black seal)For tapered 50mm/61mm OD headtubeForged alloy upper cup with CNC machined alloy lower cupStack Height: 18.8 + 2.4 = 21.2mmWeight: 110.2g.Upper ZS44/28.6, Lower ZS55/40.Spares:Upper Bearing: 160-6460Lower Bearing: 160-6470Crown Race: H6078.