Kyle Lawson has designed a versatile tube holder capable of being printed with a 3D printer.
In biological sciences, we use 6 different sizes of tubes for samples. This two part block, is the only block I know of that can accept all 6 types of tubes. I designed it so that I could split into 2 halves to be used as 2 separate racks. I’m really excited about scientists and hobbyists being able to produce useful equipment at home… provided they have access to a 3D printer.
Tube sizes that it holds include: 0.2mL, 0.5mL, 1.5/2mL, 5.0mL, 15mL, 50mL
If you are interested in printing the tube block, Kyle has made the design available on thingiverse(link below) under a CC BY-NC license