Herc Seal fittings are manufactured from galvanized steel meeting spec ASTM A-653 (Lockforming quality) for Spiral Pipe. They feature a double legged EPDM gasket which creates a virtually airtight connection when slipped into spiral pipe. The gasket is mechanically attached to the fitting with a 180 degree hemmed edge. This hem gives added rigidity to the fittings, ensures that the gasket will never slip out of place and makes a safe rounded edge for the installer.