As you can see in the photo below, there is a section of clear tube which I added a while back due to a rupture in the original black tube. (mechanics.stackexchange.com)
The drip set includes clear tubing (the fluid line) that connects the fluid bag and the needle. (statecollegevethosp.com)
Daniel Fels of the Swiss Tropical Institute in Basel grew the microbe Paramecium caudatum in complete darkness in clear tubes, which prevented the cells from passing chemical messages to one another. (scientificamerican.com)