Instruction: Answer the given question by extracting information from the supporting document.

Input:
Question: what's the size of the opening?
Document: This is a perfect container to use for pour-over coffee methods. Heavy glass keeps the coffee warm, the opening is the right size, and it is the perfect volume for 400-500 ml water pour for such things as a Hario 02.
The size of this jug is fine and fits nicely in the refrigerator. However, the lids (I bought two of these) not only are not hermetic, they don't fit at all, being too small for the opening. Since I am handicapped and have problems getting out of the house to the post office, I'll keep them, but I guess I should have listened to the other reviews that mentioned the same thing.
The trouble is, at a low-flow opening, the liquid barely pours out at all. It's like a trickle. At a higher-flow opening, the lid will fall right off if you tip the pitcher to a horizontal position. It's very tricky to adjust it to an opening that will allow flow without causing the lid to fall right off. Tricky is NOT what I wanted for use with my young children.
the lid fits great and the size is perfect for me. i had no prob grasping the handle. i will be ordering more in the future,
Love the size of the jug and that the lid has a really good seal. Glass is thick too - more durable.
We use these for juicing. Just the right size. Cover stays on very secure with a fantastic seal. heavy weight glass. Great feel.
I like this because it is just the right size to store my green juice in and most important the lid seals well so that minimum oxidation occurs.
Exactly what I was looking for. Great quality, good price, perfect size, looks pretty, lid is very easy to wash.
Wish it came in like 32 ounce size. 17 ounces is rather small. But, it's nice to have a cool square glass mug. :)
The smaller size makes it convenient to keep in fridge or bedside. The top is NOT airtight, although the listing states that it is. Other than that, I like it.
Answer: It is 2 1/2 inches.  h = 6" and w = 3"This was smaller than I thought I wanted, but it turned out to be a very handy size for many things.