Venting system allows you to quickly and easily change vent sizes on a custom earpiece. Each tree contains one of each vent size: #1 (.100" / 2.54mm), #2 (.080" / 2.032mm), #3 (.060" / 1.524mm), #4 (.040" / 1.016mm), #5 (.030" / 0.762mm) and #6 (solid plug).