Review on Efficient Stainless Steel Bullet Core Push Pop Up Bathroom Sink Stopper with No Overflow & Drain Basket by Kyle Kriglstein

I measured and found that like most household manual sink drains, I had a 1 1/4 drain. I ordered this and put it in the sink to install. I pushed the center down to stop it and it got stuck. I pulled the knot back and used a screwdriver to pry and loosen the center. I pressed it a few times to make sure it worked, then tried to tighten the center back up and it stuck again. So my guess is that the center piece needs to be loosened as it looks like the spring assembly underneath is slightly off center. You wouldn't know as there are NO installation instructions in the box. However, for $14 it works fine, I just hope my kids don't play with it and lose the centerpiece as it's loose. A few weeks update since I had to pull and use a screwdriver to pry the center back up as it's slow to tighten and then doesn't work. If it was an expensive part and didn't work most of the time I would return it. I guess I'll have to clean the drain and fix the center piece to make it work properly. Second update. In the months since it no longer sits flush with the bottom of the sink, the silicone seal seems to have hardened or something and it will no longer sit flush with the bottom of the sink drain. It still won't pop out again when the center is tight. I end up removing it about once a week because it sticks. A kind of pain. UPDATE: The seller contacted me and asked if I would like to try a new one. I said my first one was probably bad, the new one works great, bounces up and down like it should and the center button is stuck. This is much better than the previous one. Many Thanks.