This is a cost effective way of making your door compliant to fire regulations without breaking the piggy bank. I found it relatively easy to install. You will need to make sure you follow the informative instructions. You must have the 22mm between the door stop and the face of the lock as stated, or it won't close. One thing to note is this lock comes with 3 keys that cannot be copied here in Australia, so I recommend that you put one of the keys in a safe place in case you loose or forget the other two. Also the knob on the back is only for keeping the lock tongue in so it doesn't automatically lock if the door closes. (It's not for locking the handle from the inside) I was able to install the lock with a little bit of work in my original lock hole. I made up a small plate to cover the old lock tongue hole. It also comes with a sticker as shown in the photos attached.... Highly Recommended