That it's happening at some scale seems rather clear, i.e. Russian tankers either directly transfer their cargoes to EU-bound ships sailing under other flags in the Black Sea, or slightly indirectly e.g. transferring first to non-Russian tankers that have been immobile in the Black Sea for months, essentially acting as a floating sanctions-free transfer station/"port". Are there any estimates on the volumes involved? How do those volumes compare to what oil Russia exported to the EU in 2021 for instance?