One new Mann brand air filter, part number C3084 or 11-00981. This fits:
Opel 1900 Sedan & Wagon (with carbs) 09/1975 - 1977
Opel Manta 1900 & Rallye 1900 09/1975 - 1977
Opel Ascona 1900 09/1975 - 1977