Hex Head Screws with Flat Washer and Split Lock Washer
Also Known as hex head sems screws.
The flat washer distributes holding pressure and protects delicate surfaces from damage while the split lock washer adds tension to prevent loosening from small amounts of vibration. Also known as hex head sems screws, the washers rotate freely but are permanently attached. They're made from 18-8 stainless steel and have good chemical resistance. Screws may be mildly magnetic.