SES Rubber Grommets, DG Series. The HELAVIA DG membrane grommets from SES are made from black polychloroprene rubber. They can be used to protect cables and wires when being passed through panels. These rubber grommets can also be used to seal off any unused entries in panels and enclosures. Features and Benefits. Black polychloroprene rubber Available with 1 mm and 1.5 mm thick membranes Tensile strength at break: 7 MPa Ultimate elongation: >400% Dielectric strength: >13 kV/mm RoHS compliant