This design is a series of holders for 15ml centrifuge tubes.
The holders can hold 1,2,3,4 or 6 tubes. There are two versions named "compact" and "stable". They differ by the size of the legs: "compact" has smaller legs while "stable" has longer legs but take up more space.
It can print without supports but you should make sure to have a very good bed adhesion.
The shape is designed to allow to see the base of the tube unobstructed, useful when you use it for decantation.