9/16 Long Arm Alloy Steel Hex Key is a practical replacement tool when the socket needs full-flat engagement from an in-range hex key. The ASME B18.3 width band is 0.5600-0.5625 in.; the key is held just under nominal so it enters an in-tolerance socket and bears on the flats.

Replacement of rounded or worn keys helps protect expensive socket fasteners during service and teardown. Many buyers stock the Long Arm key beside its Short Arm twin so the same width is available in both geometries.

Cold Headers keeps this driver family tied to the broader socket-fastener catalog rather than treating it as a commodity tool. Review the 9/16 in. width, Long Arm format, short-leg length, and arm length before ordering. Hex Socket Pressure Plugs are a related catalog section for buyers sourcing socket-drive closure hardware.

Technical Highlights

• Style: L-shaped hex key, Long Arm
• Material: Alloy Steel
• Width Across Flats: 9/16 in. (0.5600-0.5625 in.)
• Short-Leg Length: 1.656-1.844 in.
• Arm Length: 8.906-9.094 in.
• Dimensional Standard: ASME B18.3

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.