31R125DPS, 0.312 X 1.25 Dowel Pin, Alloy Steel, Plain

A dowel pin is a solid, cylindrical pin mainly used to locate machine parts in a fixed position or to maintain alignment. Dowel pins are held in place by interference created around the entire pin circumference when it is pressed into a hole. The insertion, holding, and radial forces generated by these pins are very sensitive to hole diameter variation and usually require the use of a reamed hole.

ASME B18.8.2