Based off a similar holder used in the lab I work in.My main motivation for designing this was that the racks for 15mL and 50mL available in the department was essentially an enclosed box which made it difficult to properly see the contents and also difficult to ensure proper sterilisation of the inside surface.The goals of this design were:- Be open so that it is easy to disinfect with 70% ethanol spray- Easy to see the contents- Configurable in various sizes and form factorVariables are listed at the top of the SCAD file and are described by comments. Default values are currently for 50mL tubes and 'support' refers to the vertical protrusions that hold the tubes. With 15mL tubes I use 16 as the tube diameter and 6.5 as the distance between tubes. I have only printed and used the 15mL variant but from that experience the 50mL variant should work as well.Updates planned: Simplify selection of 15mL or 50mL variant, Add wings to stabilise single row/column racks.