Unlike other dowels, our SPAX dowels are perfectly matched in geometry for use with our wood screws. They are made of nylon, a special dowel collar protects the surface of the building material and prevents the dowel from disappearing in the drill hole. A rotation lock also prevents the dowel from turning when the screw is screwed in, making it impossible for it to spread. Our anchors are also suitable for through-hole installation of slender components. They can be used in concrete, solid brick, solid clay block, vertically perforated brick, perforated clay block, aerated concrete and natural stone with a dense structure. For you, this means: One hundred percent hold in almost all building materials through the perfect combination of anchor and screw.