This Doctor's Advances mouth guard is shaped a little differently and is wider in the back than my usual guard. It touches the inside of my cheeks more in the back. Even trying to re-shape/re-molding them didn't fix that issue.
The front teeth section doesn't have much cushion under the top teeth (between the top and bottom), and it doesn't have much material to cover in front of the teeth, which feels strange at first. It feels like the "protection" is minimal and not as cushiony as other guards.
The cushion in between the top and bottom - the portion that is supposed to cushion in between your upper and lower jaw when you bite down doesn't have as much soft material.
When you form the guard, and are biting down, the teeth go right to the bottom harder tray of the guard. So the cushion factor is minimal and you're just biting on the firmer portion. The "cushion" area seems to only be for shaping around your teeth and not so much to extra-cushion your bite.

The length of this guard is not too long for me. It doesn't go past my back molars. It actually stops just before the last molars on each side start. (You are supposed to be able to trim off the back if it's too long for you.)
Although the tray stays on when I open my mouth, the back section lifts off, mostly one side. I couldn't fix that issue.

The other brand of guard I typically use doesn't have these issues for me. I guess I already found the better product for me and will go back to that one.

I have TMJ and mouth guards are a must have for me. But they can't be too big or clunky and they have to allow my teeth to be cushioned to combat my night jaw clenching as well as keep my jaw from tweaking out of alignment. So the cushioning has to be even and properly form to my teeth. I started using guards nightly many many years ago when my dentist kept pushing me to use one. (Best thing I've done for my teeth/jaw!) I couldn't go with the multi-hundred dollar one they offered, so I looked elsewhere.

I used the guard for sleeping in last night. While I did get used to it as it stayed in place, it did mess up my jaw alignment a bit.

Overall thoughts: I think this isn't the best option out there, at least for ME. I don't think it would be great for those with medium to small mouths or those who really bite/clamp down their teeth while sleeping. While basically all guards say to check with a dentist or just not to use them if you have tmj or alignment issues, others other brands are ok for these issues but maybe not this brand/style. (If I don't wear a guard, it's worse for me.)
Perhaps it's best for those who only grind(?), not clamp down, and for people who have wider set jaws.

(*The guard I've used for years, and will continue to use, is the Dentek full mouth/tray style guard. The full mouth style is what this one looks like, as opposed to those that only have the cushion for the back teeth.)

This is currently serving as my nightguard until I can afford to have a dentist-made one again. It does the trick for a little while, but it will not hold up long if you are an extreme teeth grinder or clincher. I clinch my jaw pretty tight at night and have been using this for a few months. I expect I will need to replace it soon because I can tell that it is definitely wearing down.

Fine choice if you need a temporary night guard or are comfortable with replacing it regularly. It was also pretty easy to mold. Be very deliberate with molding. The bite in mine ended up being a little far back in the tray so it creates quite the lip bump when I have it in. There are instructions to remold if you want to; I recommend doing that immediately if it doesn't turn out right. The only reason I didn't is that I needed it that night to protect a recently repaired chipped tooth from chipping again. The tooth has been repaired several times and was chipping every couple of months; so far going on 4 months now & no chip, so I am pleased with this guard.

I also really like the case it came with; it has three holes for air so that the case doesn't get too funky from water gunk.

I am a fan of this product, though it did take some getting used to. It took a couple of reheats to get it fit to my top row of teeth, but it still felt bulky and I found that sometimes in the night I was actually either spitting out or removing the guard only to wake without it. So, I then decided to try wearing it on my bottom row of teeth instead. I had to trim it a bit and when I reheated it I left it in the simmering water for a minimum 5 min to make sure the soft portion was as moldable as possible. It was so much more comfortable because I could keep my lips closed around the guard without effort. In fact, after getting it formed to my teeth I actually forgot about it and left it on for another hour or so!

I grind my teeth and regularly have to get a new mouth guard because I literally chew through mouth guards while sleeping, so I have made a lot of these for myself. This specific product is not worth buying. I threw it away after making it. The tray to mold it in has so little side support that the soft plastic just squeezes out over the edges... so the roof of my mouth would have been well protected but nothing else. The molding tray also has no way of molding the soft plastic over the front of your teeth, so you are left with an uncomfortable ridge sticking out at the bottom of your front teeth. Just not well designed.

As a previous reviewer wrote, one size doesn't fit all. One of my molars wants to rest outside of the hard plastic material that the moldable plastic sits in.

I have used Doctor's for decades, and generally was happy with how easy they were to fit and how long they can be used before a new one needs to be made (thanks to the previously-mentioned hard plastic). They also are superior to the cheaper Dentek guards.

But either they've changed the dimensions since I started using them, or my teeth have moved, as now it is no longer a one-size-fits-all item. If this fits your teeth, I can heartily recommend it. If it doesn't, you'll probably want something that allows you to mold the entire guard around all surfaces of your teeth.