These sleeves are designed to fit on a standard 1-3/4" round oar shaft.
To put the sleeves on your oar shaft, slide the cover off as shown below on the left. Then slide the sleeve over the oar shaft and replace the cover. If your oar has a larger loom and the sleeve won't slide down the shaft, it can be spread as shown in the photo below, right.
The rowing or stroking flat of the sleeve should be set parallel to the tip of the oar blade.