Ikea Besta shelf on the wall?

Good morning,

we bought a cabinet combination Besta Vara. Now I somehow have problems getting the 2 shelves mounted on the wall. According to the assembly instructions, you just insert 2 plastic parts in the back and then drill a 10 mm plug into the wall through them - however, I wonder how that is supposed to hold?

Does anyone have a better idea?
It's about the two shelves above the TV

Hello, the plastic things are really not very trustworthy. I do not know it in the original, so I cannot judge whether it is better. Since you have cabinets on the side and all are screwed together, the load on the suspension is of course not that great.