By "intruments à vent à embouchure" the seller seems to mean brass instruments (labiophones). The mouthpiece (embouchure) is from a cornet or fluegelhorn.

Nosy fools (such as I, if I had the chance) will be "trapped" to use the mouthpiece as if it led to a real instrument. The seller guarantees an "effect", which may be some "raspberry" sound, possibly modified if the player shuts some of the tubes with her/his fingers.

If someone invests/wastes the €300, tell us what happened. 0 offers so far, scarcely surprising.