Frame mounted E3D V6 nozzle holder for the Prusa i3 mk3s+ with a reference on the print identifying the amount of dots on the outside of common nozzle sizes. Use 2 m3x10 screws to secure it onto the frame. If another screw length is used make sure it doesn't interfere with moving parts. Nozzles are supposed to twist in with gentle force. Use PLA. I highly recommend using a sharpie or similar to mark where specific nozzles will be stored. I also recommend supports although they are not required.
The author hasn't provided the model origin yet.