Feature:1. The outer headsetis made of aluminum alloy, adopting T6 heat treatment, CNC technology, light weight and constant strength, built in ball bearings, efficient operation, long lasting silence.2. The metal bearing can rotate 360°, high accuracy, high speed, and accurately fit into the front tube, smoothly and freely.3. Integral sealed bearing keeps the lubricant in the bearing, dustproof and waterproof, prolongs the service life, suitable for harsh riding environments.4. The rubber waterproof loop is made of high quality rubber, and a layer of waterproof loop is added to the headset cover to prevent corrosion, water, and sand, and have a longer service life.5. The universal version of the straight tube and tapered tube of the bicycle headset, suitable for the inner diameter of the upper tube of head tube is 44mm/1.7in, and the inner diameter of the lower tube is 52mm/2.0in.How to Use:Product Sequence Description (from bottom to top, the headsets are installed on the upper and lower ends of the frame head tube): Bottom File(30mm/39.8mm Switchable)‑Lower Bearing‑Lower Headset‑Upper Headset‑Upper Bearing‑Urgent Loop‑Headset Cover‑Sunflower Top Cover Kit.Specification:Item Type: Bicycle Double Bearing HeadsetMaterial: Aluminum AlloySpecification: Approx. 44-52mm/1.7-2.0in (Straight Tube and Tapered Tube Universal)Applicable Situation: Frame Head Tube: Upper Tube Inner Diameter 44mm/1.7in, Lower Tube Inner Diameter 52mm/2.0in. Front Tube: Upper End Outer Diameter 28.6