- Duro Dyne Insulation Fasteners provide a means of securing duct liner to the duct work. They are available in a variety of styles, which all feature a precision formed point to insure constant penetration of the duct liner. Once the duct liner is pierced, the fastener is in firm electrical contact with the duct work and the pinspotter current securely welds the fastener in place. Duro Dyne Insulation Fasteners are for use with MF, PBF, FG, RH, FGMH, and HSMH pinspotters.