Want to fly higher? Once you run out of string, you can carefully tie on another reel and unclip from your first reel.
1000 feet (305m) of 110lb test (55 kilo) Dacron line, pre-wound on an 8" hoop winder so you can keep it reel.
Part of the Public Laboratory Balloon Mapping Kit.
To learn more about balloon mapping, check out the open source documentation on the Public Laboratory website.