A plug connection for fast-fit coupling of two appliances forming part of a medical handpiece system includes a first coupling fitting on one of the appliances and a second coupling fitting on the other of the appliances. The first coupling fitting has a movable locking element and the second coupling fitting has a projecting element projecting toward the first coupling fitting. The projecting element comprises an end portion of a media line or an end portion of an electrical contact and is positioned to engage a surface of an opening in the locking element to move the locking element between lock and unlock positions when the first and second coupling fittings are moved toward and away from each other.