The Caliburn Concrete Screws by GRK is easy to use and "UberGrade" as the manufacturer likes to say.
Use 4 screws per anchor. This fastener rates 2120 lbs/in of Tension Pullout and 2055 lbs/in of Shear strength in 2000 psi concrete.
¼" x 2-¼" Handy Pack contains 50 screws.
19/64" x 3-½" Handy Pack contains 25 screws.
Includes: T30 star drive bit and concrete drill bit.
If your concrete is very old or anywhere the concrete contains higher granite composition you will require a high-end drill bit. The drill bit provided is medium quality and not designed for extreme concrete density.
These fasteners are just short of miraculous. First, they came with bits to screw them in and a drill bit of exactly the right proportions. Not only are they extremely strong with excellent grip, they can be pulled out and re-tightened easily. I had no broken fasteners.