Internal-thread-locking version of the heavy-duty inserts. These general-purpose threaded inserts have a thick, heavy-duty thread wall. Key Inserts are ideal for thread reinforcement, especially when the mating stud or bolt will be removed frequently. These stainless inserts provide strong, permanent stainless steel threads in any parent material, ferrous, non-ferrous, or non-metallic. Key Inserts are also well suited for quick repair of stripped, damaged, or worn threads. Locking keys positively prevent the insert from rotating.

This feature uses a modified internal thread to prevent the installed bolt or stud from rotating. This feature is useful for one-time, permanent installations.
| Item | Material | Heat Treat | Finish | RoHS |
| Body | 303 Stainless Steel | - | - | ✔ |
| Keys | 302 Stainless Steel | - | - | ✔ |

| Internal Thread | External Thread | Length(inch) | Shear Engagement Area (sq In.) |
| 3/8-16 | 9/16-12 | 0.50 inch | 0.384 sq in. |