STL Files for the 3D Printing of a Customized Spectroelectrochemical Cell for Magnetic Nanostirring Applications on the SPELEC Instrument (Metrohm) This dataset contains STL files for the 3D printing of a customized spectroelectrochemical (SEC) cell specifically designed to enable magnetic nanostirring during SEC measurements using the SPELEC instrument (Metrohm). The original design was created using FreeCAD software. The printed cell used in experimental studies was fabricated in black polylactic acid (PLA) using an XYZPrinter da Vinci 1.0 Pro equipped with a 0.4 mm nozzle. The design includes two modular parts forming the main cell body, incorporating a 4-pillar structure to ensure proper sealing and minimize external light interference during measurements. This configuration allows for the use of magnetic nanostirring with sample volumes as low as 50 µL when placed on a standard magnetic stirrer platform. The closure mechanism in this design provides an alternative to the standard commercial SEC cell, which uses a magnetic coupling closure system that is not compatible with magnetic nanostirring under equivalent experimental conditions. The files are provided in STL format and can be directly used for additive manufacturing using common FDM 3D printers.