This is a tube holder for small centrifuge tubes, or eppendorf tubes, that holds 6x3 tubes. It has deep lower wells to prevent tubes from slipping, and drainage holes to prevent any liquid buildup. 

Design is meant for low material usage and quicker print times. 

The legs should snap into the sockets firmly, and stay in via friction. Depending on your filament, you may need to adjust the dimensions by a small percentage, but current size should be well tuned for Bambu Basic and Matte PLA, as well as Polyterra matte PLA.