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

Input:
Question: What is the black circular ring at the top made of?  I'm trying to avoid a pot with plastic parts. thanks.
Document: So, I now use pour over. I've got a Melitta cone which I found at a coffee shop. I wanted to use that cone with some kind of pot or server made of glass so that I could see how much coffee I'm making. The glass pot that came with my coffee press had a handle that got in the way of the cone sitting flat on the pot.
This is one of the cheapest made items I have ever bought. You literally can't put it onto certain surfaces or let it come in the slightest contact with other items in your sink, it will crack. You're better off getting the 02 and pouring it into a heavy duty tall ceramic mug. Avoid the 03 at all costs.
Despite washing this server immediately after using it, the rubber seal part of the top quickly acquired a bad smell. I kept walking past the kitchen counter and smelling cat urine. After checking the floor with a black light (under which cat urine glows green) and finding nothing, I realized that the smell was coming from the server.I know that no one else has mentioned it here so maybe I had a faulty rubber seal but several friends agreed that it smelled exactly like cat urine.
Each piece of the V60 system is very high quality and this carafe is no exception. Be advised, you will pay a premium for the craftsmanship. This system is small, not made for bulk coffee guzzlers, but large enough, and beautiful in form and function. The only criticisms I can make are the glass is a bit thin, the handle seems a bit fragile, and it doesn't hold the heat for too long. The glass lid has a snug rubber ring that seals nicely.
I like this product a lot but it has a design problem that makes it somewhat dangerous to use. The funnel shape can result in boiling water suddenly, and explosively exiting the container when steam generated at the large bottom tries to rise up through the narrowing column of water above. This can spray boiling water all over. DO NOT put a lid on this pot when boiling water. The pot is called a "server", so maybe it is not intended to be used to boil water, I don't know.
It only holds enough for 2 mugs for me, but when I do pour over, its good to be able to have a bigger container. I feel I should I get the stand. I haven't had any issues with it but the glass feels so delicate and I've just been placing my pour over cup on top of it and I feel having the stand might be better.
Here is a portion of that review:...&#34;I broke the lid. Yes it was my fault, and I take ownership. My reason for mentioning is that the lid fell of my jar used to dispense fresh beans, and it is only 5 inches or 12.7 cm tall. It fell the short distance and cracked on my tiled counter top. Take this as advise to be careful.
Whether I'm preparing my coffee or serving it, this server is a great way to get the coffee out of a french press or for brewing your pour over right in. It is beautiful and I recommend the purchase to everyone. One item of note. The lid is a little fragile, be very careful not to drop it into the sink with other dishes as it will crack pretty easily.
I love this carafe. Its thin and light, but not even a little bit fragile. This is a very high quality piece of glass, and honestly, I would like to buy one in every size they make. Its a beautiful object, one that I plan on keeping for a lifetime. I'm even going to buy the matching double-wall glasses to go with it.
As another reviewer stated, this is simple but elegant. I use it every morning for my pour-over coffee using a Hario filtercone and white filter. It holds two good sized cups of coffee and brewing using this method makes coffee as good as it gets. I'm retired, but previously I used this method on weekends because I love a great cup of coffee.
Answer: It is made from silicone.  It holds the lid onto the pot - not a tight seal like a gasket would create, but it keeps the glass lid from knocking into the glass body of the pot.