These things are a nightmare. They don't stay on the buckets well at all. So when you go to pull up the pump they pop off, you need 2 people to work them. One holding it down and another pulling the pump part up. I got them to use on a 5 gallon bucket, they basically just sit on top and there is no way to get a good seal. Looked everywhere online (because the directions that come with them are very vague) on how to use them, and found I was using them right but still no luck. They also started to leak around the top after about the 2nd or 3rd use. Ended up pulling them off and throwing them out. Cheap so I guess you get what you paid for :(

it works and its cheap but I am having trouble with it leaking a bit when pumping.

I think the pump properly works well but it does not work for my purpose. This is a pump that you have to pull up in order to load up the pump with liquid for dispensing when you push down. It took a lot of force to pull the pump up. The product description did not mention it. I was looking for a simple pump that would dispense every time you pushed it down without the need to pull it up to load liquid. So it did not work for me and I returned it.

Works great for what is is, nothing fancy and I had to get a little creative to get it to mount in a 5 gallon bucket lid but it's earned its keep pumping 10w30 if you can't get the pump far enough in the hole of the bucket to screw it down use a dermal and sanding wheel to massage the flange on the bucket down flush and I had no more problems

I bought this for a 5 gallon pail of surfactant I use in my shop. The instructions say:
Pail Adapter Installation: 1. This adapter is made to fit senior (metal ring) flex spout closures. 2. screw adapter onto male threads at bottom of pump and tighten to secure.
I have NO IDEA what any of that says; as the reference pictures it refers to are also less than clear. HOWEVER, with a little bit of critical thinking like I said - I removed the plastic adapter that came with the pail - so now there is just a hole. I removed the bottom part of this pump (the part that screws onto metal rings), and it fit perfectly and slightly snuggly into the hole in the pail. I haven't used it yet, so I'll update once I see it in action. Fitting it onto your pail will take a little work.