5/16-18 x 1-3/4″ Security Machine Screw – Flat Hex Socket Head – Alloy Steel – Black Oxide – 100 Pk Best Choice

Security fasteners provide an added level of security by their drive design that prevents removal with ordinary screw drivers. Maximum torque transfer & positive tool engagement means easier drive installation with less pressure & slippage. Requires matching driver bit.
Flat Head screws install flush with metal surfaces or countersinks with softer materials for a clean appearance.