The paddle wheel, pin, and o-rings are normal wear items. Typically, in clean water, they will deliver many years of service. Silt/grit, chemicals, and high flow rates will shorten the life of these items. The replacement procedure involves pushing the old pin out with a drill bit or similar small diameter rod. Then you install the new paddle by pushing the new pin back into the slot. The o-ring just slips off and on with relative ease. The same paddle wheel kits are used for both the Pipe Mounted Meters and the Detached Display Meters.