Thread Size:1/4-20 | Hex Drive Size: 7/16" | HIGH QUALITY MATERIAL: 100% Stainless steel 304(18-8) which is superior to regular steel and any zinc plated fasteners, provides good strength and corrosion resistance in bad environments. | Will NOT COME LOOSE: With a nylon insert inside, the lock nuts greatly reduce loosening under vibrations and torque. | GUARANTEE: Eastlo Fastener is sold exclusively by Eastlo online. We are so confident that we offer the best competitive fasteners in the world. Satisfaction guaranteed. Money back or exchange