CONFAST 1/4" x 3-1/4" Hex Head Screw Anchor (100)

Had 17 to drop into 6 total 16x16x4 precast cement blocks. Didn't use the bit that came with the screws because I have an SDS hammer Drill. Using a 3/16 x 6" bit that I marked at 3.5" pre-drilled the holes to 3.5" ea. of the 17 screws dropped into the 4" blocks, 3 of screws heads snapped off long before the screw could have bottomed out. Ended up having to drill 6 more holes as I had to move 3 of the 2 hole brackets in order to ensure the fencing structure was properly anchored. Compared to Tapcon, they are slightly less expensive for a similar quantity in my experience, but also slightly less durable. Perhaps quality control is less stringent, so If you hate having additional unwanted holes in your work projects, you should probably consider another brand. If the holes won't be visible and you can afford some errors, then these will work just fine.