2006 New York Code - Firm Offers.

 
  Section 2-A-205. Firm Offers.
    An  offer  by a merchant to lease goods to or from another person in a
  signed writing that by its terms gives assurance it will be held open is
  not revocable, for lack of consideration, during the time stated or,  if
  no time is stated, for a reasonable time, but in no event may the period
  of  irrevocability  exceed three months. Any such term of assurance on a
  form supplied by the offeree must be separately signed by the offeror.