Instruction: Analyze a question and its supporting document. Predicting answerability based on the information provided in the document. Output yes if the document contains relevant information to answer the question, otherwise output no.

Input:
Question: What is the size difference? Are the sizes wist sizes? (I know this might be a dumb question, but just checking?)
Document: I believe that is the only difference but the new bottles are much better. They redesigned them because of the issue.Otherwise, works well if you cinch it pretty tight around your hips. If you're in between sizes buy the smaller size.
Plus the puch cover closes securely with velcro.5) As far as sizing, I think it is a good idea to go to the store and try on the different sizes. I am about 5'8" and 153 lbs (male) and my pants/shorts are usually about 30-31". I tried both the medium and the small. Believe it or not, the small fit a lot better. I know everyone is saying that this item runs small and to get one size up, but this advice would not have worked for me.
After reading lots of reviews recommending they tend to run small I went with the Medium sized belt. It fits perfectly and a small would have definitely been too small. I decided to actually measure the belt to let readers know what the belt size really is. Mine is a medium which is for sizes 32-36. The belt unstretched is exactly 37" long from end to end. The velcro is 4 1/2" on one end and 6 1/2" on the other end, and it starts right at the end of the belt.
Granted, with the phone, I was not able to get much more in the pocket. I might have been able to get a GU packet in, but I had other pockets so I used those. It was also easy enough to pull my phone out while running if I needed (to switch songs, not talk). I didn't feel the water sloshing around. The top was easy enough to open and close with my teeth. Worth the upgrade to the 10 oz. bottles. Pink is super cute too!As far as fit, I read all the reviews and still didn't know which size to get.
and that was the spot it finally worked. the down size of it is when climbing up  stairs o make a short jump, it gets in the way of your thighs, but i wasnt left with much of a choice.recomendation, or nathan makes this belt to wore it on the front, or buy a smaller size, i am a large or even extra large i generally o sizes, a order a large and was left out of magnetic zipper trying to fasten it, i do think a smaller size wont do the trick or you will be left with no circulation on the waistthanks for reading this i know is long but i hope is use full
I have used this belt for the past two weeks and am very pleased with the product. The belt itself is secure and does not move or loosen during my runs. If you are between sizes I would probably order the larger belt.The front pocket has a velcro closing and a clip for a key. The security of the pocket was one of things I was unsure of before making the purchase but was satisfied with it once I inspected the belt. I have a larger phone that does not quite fit in the pocket but an iPhone might fit in.
PROSIt does the job. Comfortably holds mobile phone, keys, gels, bank card, ID & 20oz worth of water and/or electrolytes. Secure, adjustable, stretching Velcro connection. Great for shorter long runs.CONSThe positioning of the bottles make cause some arm strikes. After using this for a year, I prefer one larger bottle. Smaller folks or women might prefer the two small flasks, though. It takes a bit of extra care, double-checking and paused runs to ensure the caps are on tightly.
SO now I have at least 2 1/2 inches of the velcro belt hanging off. I still have about 2 1/2 inches left of velco that is keeping it together. I don't think that reviewer tried running with it before writing her review (or else she wouldn't have been able to return it). I probably would have gotten a small because it has to be snug to prevent it from riding up. When it rides up, you can really feel the water bottles sloshing and bouncing. I also know that I'm gonna lose more weight as I continue training for the marathon (which is something that should be considered as well).- Comfort while running: Since this is my first time wearing a belt, I noticed the difference at first because it was technically an additional 1.5 pounds around my hips (20 fluid oz of water and then my key and iphone).
The Nathan Speed 2 waist pack has made a huge difference in my 4+ mile runs. The 20oz lasts me for about 5 miles. I fill 3/4 of each bottle with water and freeze it the night before then top it off before I run. This keeps the water cold for about 4 1/2 miles.The size isn't what I was expecting. I wear a size 36 pants so I ordered a large and it doesn't fit tight enough. The large allow too much movement of the pack no matter now much I tighten it (about 6" of Velcro on each end).
Tested this product for a long walk-run today. Went very well, even with the bottle-half filled. It did not bother my running at all. The belt sizes tend to run small so for a petite 30 inch waist guy like me- I got medium. So just go with a size bigger.
Answer: yes