Hangon Single Side Double Flange Plugs are made of silicone. They are designed for use on welding nuts and similar applications with sizes M8 up to M12. Use Single Side Double Flange when work pieces can only be accessed from one side. Each plug comes with two flanges to seal from both ends. Every Single Side Double Flange Plug is long enough to handle with ease. Simply pull in place and hole entrance will be masked from both sides. Single Side Double Flange Plugs are extremely durable. You may use a push wire to push the plug into place.