Diameter: 20mm
Length: 40mm
Material: Steel
Finish: Black Phosphate
Head Style: Hex (#30 Wrench)
Thread Size: 2.5mm (Coarse)
Thread Length: Full
Hardness: Class 10.9
Type: Cap Screw
Specifications: DIN 933

Box of 15.

A hex cap screw has a hexagonal head, designed to be driven by a wrench.