I buy from Amazon every week, and leave reviews when a touch is way beettr than expected. I had dental trays made for $300+, but they broke. I still had the whitening gel, so was about to make new trays; another $300. I chose to order these to see if they were nearly as excellent' or excellent enough'. Turns out, they are as excellent as! really. The tray is to mainly keep your lip from wiping off the goop, but they also need to be somewhat close so you don't waste the gel. These were way beettr than expected; I'd say there is absolutely no reason to get trays at the dentist or to try the home tray kits where you mail them in. The only thing about these that some may not like is they just cover the adjoin 8 teeth if you have huge teeth; maybe 10 if you have less vital teeth. They cover 8 for me, but that's all that are visible anyhow. The material is thick and seems very excellent quality. Some tips; 1) cut the top from the bottom. the instruction says it works either way, but if you heat them together they stick together. 2) once water comes to a boil, drop in and pull out at the count of three; and that is without pausing!! they turn to goop. I'd suggest you do the bottom alone (do it first) since its not as crucial of you blow it. But you get two sets, so that is some some relief if you screw it up. Just don't reckon I'll count to four, just to be sure . You are beettr off counting to two and then trying again. 3) practice sucking out the air once they are in your mouth before you boil them. It takes about 5 seconds to be a master at it. 4) once you boil and place in your mouth and suck out the air, run your finger along them. I don't know if it helps but it can't hurt. and 5) be careful to center the middle to the middle of your mouth; this sounds obvious, but since they only cover 8 teeth (maybe 10?) if you get it off, then it covers 3.5 or 3 on one side, and that is not enough (at least for me), so I had to redo it. The mistakes I made; Tried to boil without cutting, so they stuck to each other (so cut them apart), didn't center them (so I had to redo). I heard the silcone ones are lousy, by the way; they don't seperate, you can't talk, saliva builds up, etc. These have zero problems. You can talk. You just can't eat! Save some money!!