The general purpose of these designs are described in “Electrolysis Activation of Fused Filament Fabrication 3D Printed Electrodes for Electrochemical and Spectroelectrochemical Analysis”, which is published in the journal Analytical Chemistry. DOI:10.1021/acs.analchem.9b01331 This particular part is a cap to be used with the "electrolysis cell" and the "electrolysis electrode". We recommend printing this design with ABS filament.