For the Medical Mars challenge I did a test tube and a petri dish. The test tube is about 12 centimeters high and about 1.5 centimeters wide and the petri dish is about 1.5 centimeters high and 8 centimeters wide. I choose these two items because if the astronauts needed to examine different substances on Mars or examine their blood they would be able to. You wouldn't have to waste space on a glass test tube which could shatter, instead you would 3D print a plastic one. You could also use it in case you needed to collect samples for references. I have found that having a test tube and a petri dish could be helpful because they are very commonly used in observation. If they were to find new bacteria they could culture the sample in the petri dish. I have also researched that test tubes can be very helpful to mix substances together. For the Medical Mars challenge I made a test tube and petri dish to be 3D printed because I found they could be very useful while on Mars.