I will show you how to repair them and how to shorten them
Step 1: What You Will Need
Some knife (x-acto or somthing similar)
Hot glue gun (optional)
Step 2: Removing Plug
Set the plug aside.
Step 3: Cutting and Refiling Marker
When you cut it you need to sand it so the cap will go nice inside.
Inside is piece of felt wrapped in plastic.
You need to cut that thing and refill it.