Forgefix cavity wall nylon speed plug forgefix nsp421 these forgefix cavity wall plugs are made from nylon and have a specially designed cutting tip to pierce the plasterboard skin they are supplied with a 4mm pozi screw and the countersunk head feature on the plug allows flush fitting of the screw to the plasterboard the screw and fixture can be removed for cleaning and decoration ideal when re fixing into existing plug or anchor holes nylon speed plugs can be used in electrical install