I couldn't find a decent compact tube rack for blood drawing and processing (in the size tubes I work with) so I made one. It is 4.75" long, 2.25" wide, and 1.25" high. There are six 13mm holes (fits standard 4cc tubes well) and twelve 16mm holes (fits standard 4cc tubes loosely and larger 10cc tubes well). The cutaway sections front and back are so if you are aliquoting serum you can see the volume that is going into the transfer tube.
I added pyramid studs because, surprise surprise, I couldn't find any tube racks with spikes and I wanted my tube rack to be functional and fashionable.
I also added a handle to my tube rack because it looked too fetishy to not make a model for the science-themed BDSM crowd that I hope exists. See my handleless tube rack for a studded, still fun version that will mostly escape weird looks