When the vials arrived - and the parcel passed Snape's usual paranoid barrage of detection charms - he picked them up one by one, holding them to the light and studying their craftsmanship. He nodded slightly, satisfied and inwardly impressed. Very few people's taste in glassware was exacting enough to meet his own stratospherically high standards for such things.
He seized a piece of parchment, cast Serpenscript, and murmured,
"Mr. Nott,
Regrettably, our paths have yet to cross in person, and so I am unable to hazard a guess as to your tastes and preferences: obviously I cannot expect the tastes of the youth I taught so many years ago to be reflected in the man you are today.
Therefore, rather than committing myself to a less than welcome gift, I would like you to consider this note an I.O.U. for a single-dose phial of the potion of your choice. If this is agreeable to you, kindly inform me of your decision by return owl.
In closing, I should like to tender the greetings of the season to you and your family.