a construction system for a connection arrangement for media lines , wherein the connection arrangement has a connection body with a receiving opening for a media line and with internal parts for interacting with the media line and providing axial guidance , mechanical locking to prevent detachment , peripheral sealing and , where applicable , internal radial support . various internal parts can optionally be inserted into the connection body , which is designed to be identical in respect of the internal contour of the receiving opening , and for a particular maximum external line diameter , in order to adapt to at least two dissimilar media lines having different cross - sectional dimensions . the internal parts are adapted , on the one hand , to the permanently identical internal contour of a receiving opening of the connection body and , on the other hand , to the cross - sectional dimension of one of the dissimilar media lines .