Fits the ThermoFlask® Straw Lid Only. Two BPA free O-Rings are included in the pack. If you have the Chug or Spout Lid, (two different sized O-rings and no straw) please see replacements here: https://mythermoflask.com/collections/frontpage/products/o-ring-for-thermoflask-chug-lid-no-tabs O-Ring installation instruction Note: This item ships via USPS First Class Mail.