The balloon envelopes used in the project are made by Raven Aerostar .
The balloon envelopes used in the project are are composed of polyethylene plastic about 0.076 mm ( 0.0030 in ) thick .
The balloon envelopes used in the project are made by Raven Aerostar , and are composed of polyethylene plastic about 0.076 mm ( 0.0030 in ) thick .