I just got my Sunlu S4 Filament Dryer and upon initial setup I realized those rubber plugs aren't going to do what they are intended for properly. I set out to create better plugs that will trap the humidity out of the dryer to make it more effective. These stoppers/plugs can be easily removed or installed when needed but will not fall out when not wanted to be removed.

Along with this modification I also made larger handles which can be found here:

https://makerworld.com/en/models/418986