Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: What is the bottom tray made of?
Document: Well made item. This was a hard to find item so I am super pleased that the dimensions listed were right and it fit my new little sink. Also like that the bottom drip pan is not built-in making it optional. Hope it holds up over time like a Rubbermaid...
We purchased a curved black swanstone kitchen sink. One of the bowls are overlarge, the other small. We found this item and fits perfectly in the small side of the sink. A well made drainer that holds quite a bit considering it's small size. We may still need to purchase a protective mat for the bottom of the sink since the metal legs sit on the sink base and are not wanting scratches.
The flatware basket and the drain tray have an unfortunate tendency to rust. Clear nail polish "painted" on the points of contact with other steel- (1) the bottom of the legs where they rest on the drain tray and (2) the parts of the frame which hold the basket - will to a large extent frustrate the tendency of the drain tray to rust.However, contact with wet flatware will continue to cause rust on the inside of the basket.
I was using the smaller side of a split sink as a dishdrain, but the piled-up dishes would shift and slide around. This dish rack offers support to the bottom of the pile, and keeps them from toppling. I was afraid of buying a flat rubber or plastic thing because of the smells and possible mold. This solves that problem too. I have a very small space, and can't use the bottom tray that comes with it. After two months, it hasn't rusted.
As noted in other reviews, the basket doesn't appear to be stainless steel. It rusts! Entire tray and basket poorly made. Cheap Chinese crap.
We were remodeling our condo and had a new kitchen sink installed. It was a split design with one large side and one tiny side. I wanted to use the small side for drying dishes and this little rack fit perfectly. I don't use the bottom tray part since it's just sitting in the sink anyway. Works great and looks cool. I hate having drying racks out on the counter so it was important to find something that would fit inside the sink. This did the trick.
Some of the reviews of this product made me hesitate to buy it. I eventually decided to give it a try. I have a small kitchen and this rack fit perfectly on my windowsill. It's true that the drain tray gets a little grungy - after all, you drip water into there and it sits for awhile until it evaporates. You can't put holes in it to let the water drain, or it would drip water everywhere ... so it gets a little slimy.
Great little product. Would have preferred it if the tray that it sits on was designed for the water to drain off into the sink, if used on drain board. I am using inside my sink, so that is NOT an issue, however, I found rubber suction cups helpful to stabilize rack and prevent any rust forming on my stainless steel sink. I think they should have been included. Plate slats should have been made deeper . . .
Perfect for a double sink. We have put our heavier & better China in this dishrack without worrying about it falling over. It does have a removable plastis bottom that you really can do without because the water will drain directly into the sink.
Bought this rack with the hopes that it would fit in the small side of my asymmetrical sink. Well it does, but it IS pretty small. I can make it work by tilting the dishes half on the rack and half on the bottom of the sink/wall of sink. First started by using the metal base, as the rack slides about a bit on  the bottom of my sink, but it quickly started to rust when water was sitting in it.
Answer: The bottom tray is made of sturdy plastic.  Overall this item is very good quality and I'm very pleased with it.