Plug `s so-called plug, allowing not see through.
There are differences in shape:
- Called Doubleflare Gauges (full plugs) have an hourglass shape, which prevents locking.
- Screwplugs (screw caps), are inserted and screwed through the broader edge.
- Plugs with rubber, in the shape and width are consistent plugs, which are attached only by a wider rubber ring on the ear.