Imperial slotted spring pin, ASME B18.8.2

Slotted spring pins are used as fasteners to secure components, particularly where there may be some manufacturing tolerance in the hole size. They are designed to flex during installation, allowing them to fit into holes with a wider range of diameters than solid pins. This flexibility also contributes to vibration damping. 

The ends of the pin have a bevelled chamfer and are designed for plain drilled holes but a countersink makes assembly easier.