Let me rephrase: This is a test tube rack designed for molecular biologists. Each module holds 16x PCR tubes or 4x 1.6 mL tubes or 4x 600 uL tubes. The modules clip together so you can assemble whatever type of rack you want. I am planning to make some adapters as well that clip into the system that allow you to use lids, etc.

PCR tubes fit quite snugly into the rack if you push them all the way down, which is nice for freezer storage since they won’t fall all over the floor if you happen to drop the rack on the ground. They can also fit into freezer boxes, allowing you to store more PCR tubes per freezer box than before.