Crimp contact. HDC insert, socket, 3000 V, 550 A, crimp connection, size: 550. A heavy-duty connector consists of a connector insert and a protective housing. The insert forms the heart of the heavy-duty connector and is responsible for the electrical function. Weidmüller connector inserts are made from high-quality insulating materials that allow for safe transmission of higher voltages in confined spaces. Additionally, we use only a single type of plastic throughout our entire range, which is UL-listed and suitable for railway applications. This enables unrestricted worldwide use of the RockStar® connectors.