Just what grandson needed for football. Had just got upper/lower braces. He said it was easy to mold. Ordered second one to have for back up. Went to practice without his mouthguard one day and resulted in 2 broken brackets plus cut his mouth up on the inside, needless to say he hasn't forgot his mouthguard since.There is nothing on the online description or on the package itself describing what makes it a "duo". There are not two mouth guards. It looks like all the rest except it looks much taller. Apparently, there is gel on the top and bottom of the guard which you can not see from the online photo or the package.I broke my jaw 6 months on the left side of my face. It took a while till I regain the strength in my jaw to where I can eat solid food. Now, I regularly go to the gym and I train with a lot of heavy sets in my routine. I have the fear of fracturing my jaw in one of my heavy sets. So I bought the mouth guard for the purpose to prevent further fractures. I personally enjoy using the guard in many of my routines (weightlifting and boxing) and it provides me the mental reassurance of my teeth are secure. They are very comfortable once it molded to the teeth and more when use them often. Depending on your jaw outline, the guard will protrude a bit but that is not problem for me. Whenever I go to the gym, I feel can accomplish heavier sets now that my teeth are protected.The value of the guard is worth it for me due to my past experience.I bought this model in the past for weightlifting. For me, I broke the left condile on my jaw so I need the mouthpiece for deadlifts, squats etc. I find the product to provide adequate/good protection when biting during my lifts and mitigate further damageNow, the mouthpiece is on the chunkier side than other so it may protude a bit depending on your facial features. This doesn't bother me.Other than that, it will get the job done when the mouthpiece is applied correctly.I can't tell you this Shock Doctor saved my mouth one time, or that it'll prevent any and all possible damage from happening to your teeth. What I can tell you is that after having extremely expensive dental work done, the Shock Doctor Adult Nano Double Fight was the least I could do to protect myself. For that it's well worth the money.The idea behind the Shock Doctor is that the memory plastic inside the lining can be shaped and will hold that shape. It creates a cushion for your teeth that's custom-fit to your mouth. They call these "boil & bite" mouthguards but really you want to use not-quite-boiling water. Follow the very well written instructions that came with it and you should be just fine. My new porcelain veneers didn't feel very comfortable in my mouth and I was worried the Shock Doctor wouldn't set right or would hurt. It set just fine, and on those rare occasions my free-sparring needs protection, the Double Fight is comfortable and protects both my upper and lower teeth while still making it fairly easy to breathe.The mouth guard seems to be of good quality but it is extremely narrow. I ordered the child one first finding it not to fit so I then ordered the adult size. It still did not fit my molars. I am disappointed it wouldn't fit because it seems so be wonderful otherwise.Great mouth protector. It takes a while to adjust after using the cheaper ones for a while, but you will. Once you get used to using these you won't be able to use the cheap ones again. I bought one for my son and I. The fit is tighter than then cheaper single piece ones. However, after a while you will get used to it.Preparation and fitting was very easy. Unfortunately, mouth piece feels a little small in my mouth. I have tried several times to use mouth piece, but it feels like I am wearing braces. The mouth piece is very good quality just too small for me.Did not receive the same item as shown in the images. I was given an alternative mouthpiece with "SHOCK" written on front, rather than the logo. Customer service was only able to advise me to return it, but could not confirm whether or not they have the one I initially wanted to begin with. They were not able to reassure me that the same would not occur if I simply reordered another one.I expect to receive exactly what I paid for, especially when spending so much. Instead, I was given an item which was not advertised at all in the description, images nor was it an option to even select. I had selected the mouthpiece in white with the logo on it, and did not receive it.I use this for Brazilian Jiu Jitsu and grappling and it works great. Since getting it I've taken a few knees and elbows to the face and have not been cut. My one complaint is that this is certainly a low profile top and bottom jaw supporting gum shield! So low profile that initially I found it quite hard to breath because of the very small airway. I'm comparing this to the old Shock Doctor Double gum shield that had more of a gap between the top and bottom teeth. That old model was thicker (so your mouth is more "open") but allowed a lot more air to pass through. For grappling I preferred the old model but for striking it's probably better to have a lower profile? If you do buy it then when moulding remember to press it into the upper jaw first before biting down. This prevents you from ending up with the lower jaw too far forwards and having to remould.Great seller and product in top condition. The design of the product itself however is not that great. It would be one of the top mouthguards, but for one problem; it is marketed as a double mouthguard, but there is hardly any protection for the lower teeth if one was to receive an uppercut to the jaw. All there is instead is unusually hard plastic and three tiny slithers of what looks like silicone. I reckon this could harm more than protect. Which is a shame, because the breathing channel is a brilliant idea and if there was sufficient lower teeth protection it would be a no brainer to buy this over others. But it is missing, and for the price of 25 pounds, it seems somewhat lame.This is supposed to be an adult size and is no where near big enough...Fitting is very bad, loose around the gums and doesn't sit well in your mouth. This leads to the feeling that its constantly tipping away from you teeth. Using this for boxing I found it completely ineffectual, took a shot to the nose and I could feel in my front teeth and the shield was leading forward and the punch roll completely over the guard. I would imagine the looseness would also be annoying if you where playing fast moving contact sports such as rugby. Avoid this completely