This is a mount for a filament runout sensor, when you use your Ender 3 in dd.
You can print it in PLA or PETG, flexible materials can make trouble.
You can mount the sensor via M3 bolts and nuts.
This is the sensor i use: https://a.aliexpress.com/_mLpMqV4
Category: 3D PrintingThe author marked this model as their own original creation. Imported from Thingiverse.