Mr. Gasket Oil Pan Bolt uses a smaller-than-standard hex head is ideal for tight spaces. Because of the hex flange head design, it will not fall back into the socket wrench allowing for easier installation. It comes with a special underhead serration which prevents loosening and the wide flange head distributes uniform clamping pressure for an ultra gasket seal. Bolts are zinc plated, Grade 5. This kit contains 14 pieces of 1/4"-20 x 1/2" and 4 pieces of 5/16"-18 x 3/4".