Coil bolts and inserts should be

• A. Compatible in diameter only
• B. From the same manufacturer only
• C. Compatible in diameter and from the same manufacturer
• D. Compatible in length and diameter

Answer: (C)

Matching diameter and using the same manufacturer is essential because the bolt threads must engage exactly with the insert threads, providing full thread contact for the intended shear and pull-out capacity. A correct diameter prevents loose fit, cross-threading, or stripped threads, which would weaken the connection. Using parts from the same manufacturer ensures the thread form, pitch, tolerances, and coatings are designed to work together, giving predictable performance and corrosion resistance. Length alone isn’t enough if the diameter or brand doesn’t align, so the safest, most reliable choice is to pair a coil bolt and insert that share the same brand and diameter.