I appreciate the model number that has not changed since long ago. Security precision will fall, but because of the 24401 key that has not changed since long ago, all the workers will keep it constant. I have lasted the longest in key switches I know. However, when it gets broken, it is supposed to be stopped by the right of the key, but it is often the phenomenon that it will be missing somehow. Although we recommend exchanging electricity every seven years, there are also some sites that are using the owner's instructions without breaking for over 10 years. Although there is a problem of cylinder scraping, I feel that durability can be reliable as it is.