5/16"-18 x 1-1/4" Zinc Grade 2 / A307 Square Head Bolts (10 pcs.)Type: Square Head Bolts
Head Style: Square (1/2" Wrench)
Thread Size: 18 (Coarse)
Hardness: Grade 2 / A307
Type: Square Head Bolt
Box of 10.
A square head bolt has a four-sided head. Compared to standard hex bolts, square bolts have a greater surface in contact with the part being fastened, and therefore provide greater resistance to loosening (though also greater resistance to tightening). Square bolts are typically mated with square-headed nuts.