Feature:1. With double bearing structure, the rotation is more stable, easier than the loose ball bearing and single bearing.2. Made of reliable aluminum alloy and steel, easy to install, and is very practical. Good alternatives for parts, make rideing easier, more enjoyable.3. Smaller upper scale angular cartridge bearing can save item weight, larger lower bearings will provide strength and durability.4. Match with 28.6mm/1.1in and 39.8mm/1.6in bottom fixing to meet your needs in different situations. Bike front fork stem can prevent the bearing from over abrasion and make it rotate freely.5. The inner diameter of the head pipe is 41.8mm/1.65in, the inner diameter of the lower mouth is 52mm/2.04in, and are also the outer diameter of the upper bowl and the lower bowl of the bowl group.Specification:Item Type: Double Bearing Bowl GroupMaterial: Aluminum Alloy + SteelApplication: for Mountain Bike, Road BicycleProduct Size: Approx.41.8mm/1.65in, 52mm/2.04inWeight: Approx.106g/3.7ozSuitable Frame Head Tube: Upper Inner Diameter of 41.8mm/1.65in, Lower Inner Diameter of 52mm/2.04in.Applicable Straight Pipe: Standard Straight Pipe (Upper 28.6mm/1.1in, Lower 30mm/1.2in)Applicable Tapered Tube: 11/8in-11/2in(1.5) Tapered Tube (Upper 28.6mm/1.1in, Lower 39.8mm/1.6in)Bottom Fixing Specification: Bottom Fixing of 28.6mm/1.1in and 39.8mm/1.6in Package List:1 x Bottom Fixing Ring2 x Bearing3 x Pressing Ring1 x Flower Shaped Screw Top Cover