With insulated lines, it is necessary to increase vents with the insulation through the addition of vent bosses and extension parts. For permeant chemistries vent bosses are used with PTFE plugs. They're also referred to as bellows or compensators and therefore are a very susceptible ingredient, a source of misspecification https://www.facebook.com/permalink.php?story_fbid=pfbid0pwn3bMdnvzTdGNCHGu7rfW4o2QaJqFfomZo2UVyCRLFqA1eDWJuLYVRQHBPHLM98l&id=61560512640678&__cft__[0]=AZUMNBbd4GLlSXNCqGI6XI9I1OckfgdIm67Oe-R9_vU5mX8g-TsVpDtN7eZdAV4VU0qiU1LgeETjkKhaLzX9VRLuAGTdBJPfBMe3rq3cnwIWtcD_ESI8pvmPOZYDq0zrNNpJ-Qqbbl411bdM5uDrtsTlXMhNogQCrnVTW8HV-6ZRfRPl_wtK2PCt3Qr04-cZU3mVUi1rWgsxNhQzLSCu1nxO&__tn__=%2CO%2CP-R