Our Thunderbolt™ branded countersunk head anchors are an all-metal self-tapping anchor, cutting its own thread into the substrate; this results in no expansion stress, meaning that they are ideal for close to edge applications. They are quick and easy to use. Suitable for solid concrete, hollow concrete, most natural stone, brick, and block. Removable. The countersunk head gives a flush finish once in place. TX drive. The zinc and yellow plated finish offers protection against corrosion.