Questions about wallpaper&plaster

I measure a diameter of 3.5mm and a screw length of approx. 2cm. But beware, it's not really a screw; firstly it's made of plastic, and secondly the nuts are more like rubber stoppers. These can be moved and tend to jam. The screw does not have a standardised thread, but you can screw an M4 nut onto the screw with a bit of finesse. However, whether this adhesive screw can hold your speakers remains