If you want to convert your Hasbro Black Series 2015 Vader Light Saber to a removable blade, this insert will allow you to do this.
I created a walk thru on how to do this. See this link on fx-sabers.com
I added little holes in case you want to add a LED inside the blade insert to light up when the blade is removed.
The part was designed in Centimeters, you may have to scale up by 10x to 1000% to load in Millimeters.