These anchors are heavy duty metal fixings. They are mainly used to fix metal plate but can be used to fix timbers as well. All the anchors we supply are displayed in the photo. Referring to this photo you will see numbers above each fixing, e.g., 8/30. The number '8' refers to the drill size you need which is 8mm. The number '30' refers to the maximum thickness of material that the anchor can fix which is 30mm. The ideal material that these anchors can fix to is concrete as there are no voids for the tapered grip to expand into like there can be with brickwork.