These 5/8" X 4 1/2" Parawedge(TM) anchors from Cobra(R) 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 the bolt and turn with a wrench and you're set. These heavy-duty anchors for solid concrete are the professional's choice.