Polyform foamfilled buoy MB-serie. This buoy is made of strong polyethylene with polystyrene foam, this standard buoy is for surface use, for underwater you need other foam. the buoy has ROD: short or long.
Polyform is already 50 years the choice of professionals and there is a good and worldwide services. working-load is 50% of volume. Applications: anchor- pick-up-buoy or marker-buoy.
In one of the picture there is a table with all measurements and other data.