A low wind session: 6 to 8 knots at the windmeter. Of course you need a good amount of foil experience to tackle these low winds.
Note: in the YouTube description, MiLF means "Made in La France", for a prototype shaped and glassed in the French headquarters. Patrice has always liked risque' references... like the spermatozoid logo :-) (or the "Couine Marie", the Perv, the Greedy, ...).