This is a fundamental building material for use in scratch-building or customizing models.
These are simple clear plastic rods, each 40 cm long (just over a foot for those of you still using the Imperial system). They can be used for just about anything you can think of that needs beams -- and they're easier to cut and work with than metal rods. Flexible, so you can bend them to a certain point, they can be heated by holding them close to a light bulb to allow you to bend and shape them a little; cut them with a hobby knife (be sure to file off sharp edges), and glue with plastic cement. Have fun!