Inch bore sizes are designated with the whole inch followed by the fraction. For example a 1.5" diameter bore would be 1-1/2. Metric bore sizes are designated with "MM" after the metric dimension (X 25MM). These bushings are easy to install and remove, these bushings fit flush into tapered bushing sprockets and or pulleys. The bushing contacts and wedges inward, gripping the shaft and bore of the sprocket. Bushings have an 8° taper, are made of steel and come with a black oxide coating.