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

Input:
Question: I just got this today, I tried to put it on my tripod but its not stable. If you use a tripod with this what kind do you have?
Document: I've tried twice now to contact the seller via their website and they have not even responded.I'm sure I got a dud because everything else about the unit is high quality. Unfortunately I can't use it and the reseller doesn't seem to care.This kind of customer service is not acceptable. It's unfortunate because I was planning on purchasing a tripod from them but won't now.
Once I purchased a similar (exact same mechanism) slider form another manufacturer and I found out it had an issue: the cart had a little tremble/ vibration when sliding, making the camera to shake up-and-down. I thought I had gotten a defective one, so I just got rid of it and tried another brand. (Fancierstudio one).
This thing seems to be very wall built, and is pretty heavy. You can use it with a tripod, or you can use the legs that comes with it,  But again it is heavy and the cheap tripod I have will not hold it steady.You can also mount it vertical for up and down shots. Overall it is a great buy and I would recommend this product.
I've from time to time checked out the latest and greatest video sliders, and pretty much arrived at the same roadblocks:  either they were out of my financial league, or they used plastic sleeves to facilitate the smooth sliding action. This one is built with roller bearings. Absolutely slick and silent movement. For the price, I didn't think this kind of movement was possible. It comes with feet attachments, but mine is mounted on a fairly solid tripod and fluid head.
I give it a 5*, its cheap, it works... Although it catches on some sections, I might put some Slick Honey grease on it and see if it helps... but other than that... I like it!
Just got this thing. There's no rust, the slider is smooth and quiet. It's not completely silent, but as i'm not doing sound i don't care.
I don't plan on returning it. I'll use it for now and eventually upgrade to something really good. For now at the level I shoot and frequency of use it is fine for me.
This is a great slider for the money. When I first recieved it, it had a slight catch when you moved it very slow. However, I just ran it back and forth a few time very fast, and it worked itself out. It is a very smooth slider, easy to use and I like the legs and stops that it comes with.
I like this, i'm sure the $800 models are worth their weight, but on a budget, this has proven to be simply awesome. It is solid, well made, does the job (use an elastic band to pull), and is reasonably long.I would highly recommend, 4 instead of 5 stars because its not perfect, and i suppose in many cases that is why you'd pay $800 for one. but, it works and works well.POLO
The head of the nylon Brake screw twisted off the first time I used it. I was also hoping the trolly would be a little tighter, but that may be expecting too much. Overall though it is solidly built piece that will not deflect under even a heavy camera if mounted on a single tripod. The more I practice, the better my results.
Answer: I have to use two tripods (on each far side) instead on the middle. It was unstable for me too.