Instruction: Given a question and its related document, determine if the question is answerable by analyzing the information in the document. Output yes if the document addresses the question, or no otherwise.

Input:
Question: Is it better to put water or sand in the base? If it is sand.. how many lbs?
Document: Sounds like filling it with sand makes it heavier. I put some wide cinder blocks behind it against the wall and this worked to keep it in place (bags of tube sand would probably be even better). You need about a foot of space behind it as the bag flexes. If you have room for it to slide around you can guide its direction with your hits and kicks (if you opt to fill it with water).
After looking at other freestanding punching bags, the Century Wavemasters seem to be the only durable ones - reviews show many of the inflatable ones seem to pop or have flexible necks that get bent out of shape. This one is basically 2 parts - the thick plastic base & tube, to be filled w/ water or sand. It seems fairly durable, partly because the force is absorbed by both the foam bag and the entire bag itself moving.
I will need to put sand in the base instead of the water I have in it now. Plus I was told to place it on the non skid stuff you use for under rugs. But it is a great workout I highly recommend
Thought this was bigger than expected as when I kick & punch it, it does move abit, which is expected. I filled it with play sand 150lbs. I don't like how the base is put together I can clearly see the seems in which they were glued together very poor I would  not trust filling this with water in case it splits
Agree with other reviews -- good size, moves somewhat as the base is not heavy. The instructions say: can fill the base with water or sand. To make it heavier, we've decided to try sand. Guess what? The opening is as big as the opening in a gallon of milk. So, the statement to fill it with water OR sand is misleading. We still put sand in by cutting the the empty gallon of milk pack and using it as a funnel to poor sand it.
I purchased this item because I wanted a reasonably priced heavy bag for my basement. Do not confuse this with a heavy bag. I've seen blow-up clowns more stable than this thing. I was expecting some movement because I actually weigh more than the bag, but this is just laughable.I filled mine with water, which should put it at 170 lbs, if the description is to be believed. I'm 5'6" and 185 lbs. With one straight punch I sent this bag flying.
If you buy this you will need to buy about 150-160 lbs of sand and a funnel to fill it. My wife used it with water to start and she was pushing it around the room. She is a small lady too, so not good. I then filled it with sand which is about 40% heavier than water and it seems good now.
I bought this for my 9yrs old son to use for karate and kickboxing. Works better then I thought it would. I hit it with all of my force and won't move an inch. The pad is strong and absorbs kicks and punches well. The only complain I have is the hole to put in the sand in is a little small. It took an hour to fill; but once filled its great. You can adjust the height so if I use it to exercise it won't be too small.
It is pretty nice for the price, and I would buy it again because there aren't that many options out there other then a kids blow up bag, and this is way better.
It works well, but moves way to much. I am going to try putting sand in it instead of water and see if that may be better.
Answer: yes