Replaced a ~19 year old InSinkErator septic assist unit with the new Evolution Septic Assist. New unit is much quitter.. Removal/installation was simple due to the lock ring design and the process only took about 30 minutes. One word of caution, disposals are heavy. Unless you have the arms of Thor, lifting it in place with one hand and turning the lock ring with the other is not doable while hunched under a sink. I used blocks of wood to lift/hold the unit in place.