I saw this one for sale. I already saw some adds on TV of similar products that can close any type of box/cup/other and to store them in a fridge.
Item: Rack Shelf Holder Slide Kitchen Fridge Freezer Space Saver Organizer Storage Box
Seller: amel9450-zmchvak (98.3% TS)
Price: C $0.99
Shipping: free
Item location: China
Order date: Feb 11, 2018
Estimated: unknown
Tracking: tracking number
Quantity: 1
Type: 10×10 cm
Paypal name: JIANGZHONGL
Delivered: Mar 16, 2018
Package: Plastic bag with bubble wrap inside. Plastic transparent bag
Item: transparent 10×10 cm piece of silicone with some bumps on it. I never managed to put it on anything. I thought it was going to be bigger somehow, it actually could only cover a cup at most. So I figured I could use it to cover a cup that I make my porridge in. But it was a fail as it doesn’t close it tightly – I just could toss it over and that’s it. And I think I lost it somewhere when I moved to a different office.
Ebay vs. Reality 
Its just fail. Either I didn’t know how to use it – but it looked straight forward, either it didn’t work.
ebay vs. reality 