Instruction: Generate an answer to the question by utilizing the information contained in the document.

Input:
Question: What is the water jug cap size (mm or in.) that works well with this pump?
Document: I was so excited about getting this pump for water! Well it worked 1/2 way down the big jug of water and now does not work at all! I am so dissappointed! Wish I could return it!
We use Sparklet for our business and tried one of these there -- worked well for over 1-year.So now we have one at home too. Tough to find a good place for a 5-Gallon jug and the pump, but we have been satisfied trying it in different spots.After pumping out the water, it does a good job of keeping residual water inside instead of dripping.Good so far at home (1 month use)
Great pump, we take it camping every year with a 5 gallon jug of water, it works GREAT!
I've had this for several months now, and I love it! It works perfectly, is very easy to get on and off the water jugs, and will pump out most of the water. When it stops pumping I pour what's left into a gallon jug, and it only fills it about halfway. Was just as described.
I am the water sherpa. Well next time, we're bringing ONE fifteen gallon jug and this product! Yeah! !
I had a few of those giant jugs of water which I couldn't really access since I didn't have a water cooler. This works very well. It's kind of funny because you have to pump the water out but it works!
Works fine so long as the bottle is full. Once it gets to about 2/3 full the water flow really slows down and it takes forever to get enough pressure to fill my 20oz water bottle. Also, the tube that draws the water up to the pump frequently comes off. Lastly, the pump does not fit the water bottle thread very well which means it moves a lot while I'm trying to pump the water. Save your money.
I first bought that stupid primo pump from wal mart and it fell apart the first day. I have had this one for over a year fit every brand of 5 gallon jug and works great! I use 7 days a week 365 days a year never failed me.
I live in a dorm and I needed some source of water so I bought a jug and this. It did not disappoint. It works perfectly!!! I highly suggest getting this.
I was skeptical at first but after trying this product, it fits very well in the 5 gallon container.Pump really works!
Answer: It works for the 18.5L jugs that are 5.5 cm in diameter.