The screws can grip and therefore cancel very fast in the masonry, especially in the concrete masonry. The boreholes should be drilled out slightly lager with a borer that has a size of 10. In addition, the dust should be removed from the boreholes. The screws break very quickly for non-compliance with these instructions.
If you don't want to maky anything wrong when fixing the chin up bar, please order the stair bolts, since they do not break so fast when (untechnical) fixing.
Product No.: BSET6