Review on 🛁 Prisma Collection Stainless Steel Bronze Suction Cup Hooks (2-Pack) - Ideal for Shower, Bathroom, Kitchen, Glass Door, Mirror, Tile – Removable Hook Holder for Loofah, Towel, Bath Robe... by Richard Deng

At first I wasn't impressed that the base was plastic. However, the hook is at least made of metal. I wasn't ready to permanently install this, but needed to do a quick test. I attached it to my glass shower door and even without prepping the surface after cleaning it with an alcohol wipe, the suction cup gripped VERY firmly. So much so that when I tugged a little I could hear tension on the shower door hinges. I also hung 2 wet towels on it and it's no problem. It comes with instructions but one thing I noticed is that it doesn't explain the 2 mystery items in the box. The kit includes 2 clear plastic pieces the same size as the base. There is a 3M sticker on one side of each of these plastic squares. The instructions make it very clear not to mount it on porous surfaces, as the suction cup will of course not hold properly if there is air in the mounting material. So I'm assuming these parts are some sort of adapter so you can use the sticker on porous surfaces and then have the suction cup stick to the plastic. I hope this is helpful!