These bushings are made of seam steel with a thin outer bronze coating. The description should state that they are steel and not bronze as it appears in the photo. The dimensions of the resulting bushings provided a loose fit due to an ID and OD measuring 10.92 mm ID x 11.92 OD and had to be closer in size to be represented as 10 mm ID and 12 mm OD . When manufacturing sleeves, the tolerance needs to be tighter.