Both the box and bags/pouches work well. A car cannot be entered or started when its keyfob is inside a fully closed box or pouch. (For a pouch, you do have to insert the fob into the pocket with the keyring and chain, not the other pocket which doesn't shield the signal.)
However, there are some issues with the Walmart listing. (A) The title is “GIRACOA 3 Pack Box with Pouch....” That sounds like three boxes and three pouches/bags. It would be less confusing to write “GIRACOA Faraday Box with Two Pouches for Car Keys....” (B) The brand “Giracoa” does not appear on the box or pouches. (C) The title includes the term “...for Car Phone....” The box might fit a flip phone, but the interior dimensions of 10x7.5x5 cm are probably too small for almost all smartphones. Same goes for the pouches whose interiors are about 11x8 cm. (D) The Walmart photo shows the exterior dimensions of the box (when closed) as 13.1x10.7x8.1 cm and of the pouches as 13x8.5 cm. However, I measured the box at 11.5x9x6.5 cm and the pouches at 14x8.5 cm. (D) The “View All Item Details” (“About this item | Product details”) page shows “Signal Blocking Boxes (3)” and “Faraday Pouches (3)” which is false as you get only one box and two pouches.