This is small attached plug for 5.5mm DC barrel jack connectors. This was used made for @sisterlimonpot's 3d printable coral bandsaw project. 

I made the flexible plug so I could maintain my color scheme but this would work well for other barrel jacks that do not come with a plug but would benefit from one. 

This was printed in TPU but other flexible would work like nylon, I would not recommend PLA or other brittle plastics for this part.