The general purpose of these designs are described in “3D Printed UV-vis Cuvette Adapter for Low Cost and Versatile Spectroscopic Experiments”, which is published in the open access journal ACS Omega. Link to publication: http://pubs.acs.org/doi/abs/10.1021/acsomega.7b01310 This particular part is meant to allow reproducible analysis of samples held in a 50 mL centrifuge tube (VWR 50 mL Centrifuge Tube, Cat No. 89004-364). This adapter can be used in most standard UV-Vis spectrometers. We recommend printing this design with a black filament to reduce the amount of light scattering.