COSI - 3D STL Collection of Surgical Instruments Due to large file names, we have chosen to use https://www.7-zip.org/ which is 100% free and compatible with WinZip. If you encounter an error using WinZip, its likely due to large file names, please use 7zip. Inside the repository, you will find an information overview "Overview.docx", a showcase video "Example video 3D instruments.mp4", STL files of 103 surgical instruments "Surgical Instruments.7z", examples of variations of the surgical instruments using Blender add-on or Python script build on the Trimesh library "Blender Part x of 8 … 7z", or "Trimesh part x of 9 … .7z". You will also find the used Blender Add On "MultiMesh.zip", measurements of virtual instruments and settings for the add-on (.xlsx), and the script that was used to perform these measurements inside a single folder, "Scripts, measurements and used Blender settings.7z". The proposed data collection consists of 103 3D-scanned medical instruments from the clinical routine, scanned with structured light scanners. The collection consists, for example, of instruments like retractors, forceps, and clamps. The collection is augmented by generating likewise models using 3D software, resulting in an inflated dataset for analysis. The collection can be used for general instrument detection and tracking in operating room settings or a freeform marker-less instrument registration for tool tracking in augmented reality. Furthermore, for medical simulation or training scenarios in virtual reality or mixed reality. The data within this work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0 NC) (https://creativecommons.org/licenses/by-nc/4.0/).