These are for doors to the outside and all in this set use the same key. I also bought several matching handles for interior doors, some with locks (bathrooms), some for closets.I installed them in a couple days at the same time I replaced the interior door handles. Took a while because some of the old door knobs were not installed correctly by the original builder, so I had to do some repair work on the doors.I was not impressed with the instructions. I thought parts were confusing, if not incorrect, but door handles/knobs are pretty much all the same, so it was just annoying.Have had them installed for awhile now, but the one on my front door is starting to show signs of being loose. I have tighten them up and all do work like they should and to be fair my front door is not the best. These do look nice and give an old door some appeal.Very sturdyWe've installed several kinds of doorknobs throughout our last 2 flip homes. These door knobs are by far the best quality. We've only had them for about 2 months, but so far so good!They work and look good but they are super cheap. Lite weight metal compared to other brands.They seemed nice and good quality, but the wind caught one of my doors and shut it hard and then the door handle never worked again. Took me forever to get the door open again just to see what was wrong which looked like the cheap metal flanges had spread apart from the impact and the gears that open the door were no longer connecting.2 handles have broken off after a little over a year!!! NO warning signs. Very cheap product!! No abuse! Very disappointed!Absolutely terrible quality. Three out of the six broke within the first week! Complete crap. Major parts are plastic and flimsy. Do not buy!