These Parawedge (TM) anchors from Cobra® come with a threaded section with standard coarse bolt threads at one end, and a parabolic shaped taper mandrel neck at the opposite end for a smoother expansion. They can be installed in bottomless holes and are cold formed for increased strength. In addition, they're easy to install. Simply drill, remove dust, insert bolt and turn with a wrench and you're set. These heavy-duty anchors for solid concrete are the professional's choice.