HiBlow rebuild kits come with a safety screw. However, sometimes the safety screw will break and the diaphragms will not. If this is the case, you can save money by purchasing the safety screw on it's own.
Fits HiBlow Model HP-80
Hiblow safety screw.
Does it have instructions on how to install
We have a youtube video on how to do it you probably need a full kit though. The screw only breaks if the magnet travels to far because the diaphragm is tore in 95 percent of cases.