Instruction: Answer the given question using the supporting document.

Input:
Question: How large is the opening for this keg?
Document: These kegs are perfect for the home brewer. They're a super nice keg, easy to wash out and seal up excellent.
Purchased this keg as a Christmas gift. The Keg was delivered as promised. The recipient found the keg packed without damage and was delighted with the outcome.
After hearing all of the horror stories about bottling your home brew beer I decided to start with kegging my home brew right from the start. This is a nice keg and I was happy to find a new one. Most corny kegs are refurbished. All the pieces were included and in good working order.
While this keg holds pressure and works and appears new, it was made in India not Italy...The precision on this keg is lacking. The lid is so tight that it requires you to use a screwdriver to get the lid off. Also the beverage out poppet is a bit off and requires a lot of force and cajoling  in order to attach the ball lock out...
I just started getting into kegging and I wanted to go with a new keg over a re-conditioned one. This Cornelius 5 gallon ball lock keg is in fact new. It came well packaged and is in perfect condition. It also came pressurized. The picture doesn't really show it...but there is a pressure release "valve" on the keg (not a pressure fuse).Side note: The Keg is made in Italy.
This is a beautiful keg and it arrived in flawless condition. I wish it had two handles on top instead of one but overall very satisfied and will probably purchase more. It actually is made in Italy like it says unlike some other items on Amazon that claim to be made in Italy but actually are made in China. I did not want to mess with ugly banged up used kegs and have to purchase new seals,etc, that's the reason I ordered this and I'm very happy with my decision.
THis is a must buy!!!! Product is beautiful. Worth the extra money for a new 1. Arrived on time n in amazing condition. Cant wait to taste what goes in it.
One thing though... this is to Amazon... add "Learn to Brew" and "HomeBrewStuff" to Prime. Paying for extra shipping when I have Prime isn't really "cool". ;-)
I bought six of these. They arrived in great condition -- only minor denting on two of them. They were shipped slightly pressurized, and they arrived holding pressure.I downgraded to a 4-star rating, only because this particular model has "in" and "out" valves that do not allow the poppet to be removed from the valve assembly.
Answer: The top is in the shape of an oval. It's not huge so we usually use a funnel to fill it. The widest opening is 4.25" and the narrower side is 3.5".