Concrete Bolts - 12 x 100 ThunderboltsThunderbolts The original self-tapping anchor with the power to be used on a whole range of construction materials, including concrete, stone, brick and block. The threaded anchor and self-tapping action allows for safe anchorage, with the substrate becoming the nut to the bolt - applying a tried and tested method for metals and wood to a broader selection of materials. 12 x 100 Thunderbolts