1.Why is the running surface so narrow? Are there wider ones? At least 25” wide. ---I am very sorry to tell you that we do not have the one that have the 25inch wide,but we can accept the OEM. 2.In what country is this manufactured? ---Made in China. 3.How much impact is there on the knees with this machine? ---I would say less then a normal treadmill . 4.If I do sprinting on this, would it bother my downstairs neighbors? I weigh 175. ---I would say no. The geometry trains you more efficiently , so there is less food slapping. Also, no motor means no motor noise, and it is sturdy/heavy so won’t bounce or rattle. I think it’s more quiet than my traditional treadmill ever was.  5.What is the limited lifetime warranty in the Rongle treadmill? ---Our products have a one-year warranty. 6.Is there anywhere customers can go to test this product out before investing all of this money into it? ---All of our products have been professionally tested. You can have a look at the video of our products. 7.can this go on a treadmill matt on the carpet? ---Yes, or even directly on the carpet. 8.Does this fold up to save space? ---The home use curved treadmill does not fold up, but it does have wheels in the front that allows you to roll it.  uld this be used to train for a half marathon? ---Sure. Do not see why not. It fatigues your legs similarly to running outside, so I could see it helpful with training. 10.I have lower ceilings at 83” would this treadmill work for me? ---The base is 17”. When you run you really don’t go up any higher then your height. So add your height plus 17” plus a couple extra inches to see if you would fit.