This is a design of a spirometer, designed to help measure lung capacity. The units are inches. It requires 2 standard size rubber bands to operate. Assemble as the picture shows. The red lines show where the rubber bands go. To use, blow as hard as possible into the open end of the device, opposite the side with rubber bands, and mark on the inner part how far out it went. Do this on Earth first, to give a calibration measurement. If the inner part goes all the way out or doesn’t move very much, use different rubber bands. In space, use it again; if the astronaut can't push the inner part out as far, their lungs have weakened, and they need to exercise their lungs more.