The Opel Astra J's factory-cast discs are closed with caps that cannot be removed by hand. You can use a knife or a screwdriver to do this, but then there's a possibility of scratching the disc.
Especially for the purpose of getting the cap and not damaging the disc is the tenant, which is forceps with the bearings at the ends. The Borticks cling to the edge of a cap, making it easy to extract it. Feature code is 8D0 012 244 A.
