Félicitations pour produits de qualité (2)

Dear [Mr or Mrs or Sirs], We have purchased your [produits] for now four years and want to compliment you about them. We have particularly been impressed by the developments that were regularly introduced in the [...] to match the changing needs of the public. Your [produits] have always given complete satisfaction to our customers, especially the [produits]. We look forward to dealing with you in the coming years. Yours sincerely [votre nom] [votre fonction]