This little plug is super easy to make and takes less than 10 min to print!
Do you have an A1/Mini and don't have the AMS system? You might notice the little black nubs where the PTFE tubes connect to the hot end vibrate and make noise during pre-print. This plug will stop the vibrating and keep dust out of them!
If you want to make sure your plug is perfectly flat, printing with a brim should work.