Semi hard plastic, non-inflatable marker buoys.
The buoy is used for all kinds of creel and trap fishing, like lobsters and other crustaceans.
The Pe3-series is produced with low-density PE material that makes it very durable. Does not require inflation. It is a hard-shell buoy and ready to use.
Also commonly used as marker buoys at watersports arenas an beaches, e.g. as lane markers.