Regular ol Paintball Barrel plug. Had one prior that wasn't working as well, so this was modeled as a replacement. No supports are required, can be used right after printing off the bed. Comment any requests for random modifications since this was done quickly without any aethetics taken into account. Works great with a 20x2.5mm O-ring or one similar to keep plug completely secure. Second version of Model (STL) is one in included pictures. Tip #1 is a larger scale of the model.