Great to tie to things like gifts, chairs, mailboxes.
Sold single with matching curling ribbon. No weight is added. Filled with Helium. Do not let loose outside.
Single 18" Star Blue Helium Mylar
Mylar balloons are a foil type of balloon, It is not used for release because they could get caught up in electrical lines.
They are expand in the heat and deflate in a cooler enviornment so may be delivered a little deflated until the balloon adjusts to the new enviornment, then they will puff up.
Mylar balloons should last 2 days but depending on the size and make they can last up to 7 days.