A rubber O-ring under the head of these screws prevents leaks and seals out contaminants. Dimensions meet ASME B18.3 or ISO 4762 (formerly DIN 912) specifications. Length is measured from under the head.

316 stainless steel screws are more corrosion resistant than 18-8 stainless steel screws and have excellent resistance to chemicals and salt water. They may be mildly magnetic.

Screws with a Viton fluoroelastomer O-ring stand up to chemicals and oil.