A great fine detail technical item that has a relatively standard headset outer diameter of 34.75mm on one end and then reduced to 32mm on the other.
This allows you to:
Gain extra clearance with short reach stems that may foul the conventional 34.75mm outer diameter spacers. 
Visually match the narrow wall outer diameter of the clamp on several lightweight stems.
Visually match some of the smaller diameter headset caps.
Specifications
5mm x 11/8" aheadset type.
28.7mm Internal diameter.
34.75 x 32mm outer diameters.
CNC 6061 alloy.
Black anodised.