I am a fly fisherman and I bought these to use in the cold winter weather for steelhead and salmon. I wear a size 10.5 half shoe and there is easily enough room for a size 12 or even 13 to use them.These socks are wonderful. I have used them dozens of times trying different things so I could write a comprehensive review. I wear them with a liner underneath and a neoprene sock over then my waders. This is the warmest my feet have felt ever. I have tried multiple combinations of the four heat settings. The weather has been consistently at or below 40 degrees. The water is 42°. The lowest setting would last approximately eight or nine hours however it is not quite warm enough. I have gradually adjusted up adding heat from the second, third or fourth setting easily being able to fish for six hours in comfort and warmth. If I were to fish the entire day on the warmest setting I imagine it would last 3 hours. On the third level perhaps 4 hours. In any event this has been a new experience, warm when fishing for steelhead.The heating pads are palpable but not problematic or distracting. The socks are comfortable. The battery packs are well above my boots and would be well above my ski boots. The app works well however Bluetooth will not function when I am in the water. When I get out of the water, they pair and function effectively. Charging works well and rapidly with a 2.1 amp charger. I'm excited about trying their other products.UPDATE 37 degrees today, river 42 degrees, used level 3 the whole time and the batteries lasted 4 hours, feet warm the entire time. I still believe it's a good purchase at $129.They work as described. No complaints in that department. The socks themselves are well made an pretty comfy. The toe cap could be stitched in place more and top and bottom heat would be awesome. But I would highly recomend them if you don't like cold feet.I would have liked for the battery life to be a little better. Wore them to a couple of football games (25 - 30 degrees F), and at the high setting, the batteries were drained by the 4th quarter. Also, they're not the most comfortable socks, and I can feel the wire running down the side/base of my foot to the toe warmer. I have to play with the wire to "get it out of the way" so I don't walk on it.See above statementI am extremely dissatisfied with this product. I had absolutely no issues and everything was great. One of the batteries and/or the right sock, turns off in under two hours. And when one stops producing heat, they both stop. I have to turn it back on and everything indicates a full battery charge.I let the battery deplete, and fully charge again m, and the same thing keeps happening. I get 20 mins to 2hrs of on time, even at the coolest setting.Extremely frustrating for a good product to not last three months.Quality - A+Material- A+Fit-B..(a little large for my size 9)Battery - C..( last about 3 hrs on med)warmth - A +..Comfort.- B..( I can feel the wires.. but not a problem for me)Overall... a good purchase and works well w the app.Would recommendI bought two pairs in the fall. One for me and the pink ladies version for her. Finally got a chance to use them this past weekend. I fully charged them and followed all the instructions for pairing the batteries. First issue I noticed is the fully charged battery only held an 85% charge.The second issue is that the socks gave zero heat. Too late to return these now and I'm very upset that neither pair works even a little. The app is also very outdated and clunky as other people have said. The wires are not small and can easily be felt while walking. The heated area is also small so the feeling on your feet is quite weird.I wanted to love these but I would not recommend them at all. If I could return them I definitely would.The only dislike is turning them on after you have turned them off. It's difficult to get under layers to turn them back on. It would be great if that could be done from the app. Otherwise they work as hopedThe quality of these socks is really disappointing - they have died while being used for a second winter season. And I have been careful with these socks given how much I spent on them - they were either hand-washed or placed in a mesh bag for delicate laundry if they were put into the washing machine, and always air-dried/never put into the dryer. These socks were purchased to wear in ski boots at the start of last winter, for a competitive downhill ski racer, which means many days of all-day training even in extremely cold conditions. There was an initial problem with one of the batteries that came with the socks (it would not charge fully), but the company did eventually rectify this issue by sending replacement batteries (I say "eventually" because at first they sent the wrong type of batteries, and so we could not use the socks while waiting for the correct batteries...). Once we had functional batteries, the socks and the bluetooth app all worked well for the first winter, but the socks have now stopped working during the current second winter season. Even with fully charged batteries, and checking that the app is connected and working (and also checking that the wires are properly plugged in), it looks like there is a problem with the wire or plugs that connect to the batteries?? After a couple of times wearing the socks outside and realizing that they are indeed not providing enough/any warmth, I did a test of wearing the socks at home on the warmest setting: there is zero heat, and the battery power still shows as 100% even hours later. The batteries are not being used at all, as indicated by the battery's indicator lights when I plug them into the charging cords.I really like the idea behind these socks, they would have been really useful for me. However the right sock doesn't heat up, and it also disconnects and turns off, even though the battery is full. The other sock heats up, but is very very weak heating, even on max level. Maybe my pair were defective, would love to try another pair, but there is only a refund option.Seem good but wanted something with remote control