Philips Sonicare Teeth Whitening Kit, Clinically Proven to Whiten up to 4 Shades, Low Tooth Sensitivity, 9 Treatments, 2 Customizable Mouth Trays, Teeth Whitening at Home, DIS132/63

I wavered between 3 and 4 stars for this one because the thing that bothers me might not be an issue at all for someone with a different mouth structure. Ultimately, I went with four because it works as advertised, though comfort for me was a problem.The best part about this kit is that the whitening power is good and it will last for a while, so the price per whitening is relatively low. Just a little dab of gel goes a long way.One weird/annoying thing about the amount of gel to use, though, is that they say there's an indicator on the side of the gel syringes but I do not see one. I just guessed on the amount, based on past experience and the practice sheet that was in the box. It seems fine. Based on what I've used so far, I think I'll get more than the 9 treatments it says it provides.The paper shade comparator was useless. My teeth seemed to fall somewhere between 1 and 4, which feels like way too big a range for it to provide any value. It doesn't matter, though. If they look whiter, that's all I care about.I've had both custom trays and the Opalesence ones in the past. Both of those were much thinner than these and I would argue even the non-custom Opalesence trays were more comfortable. That's my biggest complaint. I have a pretty sensitive gag reflex and the thickness of the plastic doesn't leave a lot of room for my tongue, which gets pushed back and makes me gag. This happens 1-3x when I'm whitening for about 20 minutes. When I was forming the trays, I tried to thin the plastic as much as possible so that both trays almost cover my back molars on top and bottom, but the plastic cooled too fast for me to get it more comfortably thin. I also used up the first set of trays (they do say they provide extra specifically if you mess up when molding them), but thankfully mostly figured it out for the second.I appreciate that these are reusable and that I can control the amount of gel I put in, especially because my teeth are sensitive. I don't love how fiddly the setup is, but given that I don't need a huge jump in whiteness, this kit is still a good value for me because I'll get a lot of whitening sessions from it.