You don't need to overthighten as it is a Nylock which will not come
undone.

The photo shows our Stainless Nut and bolt on the right compared to the standardone on the left.

Replaces the bolt fitted to the Deluxe or Thumb hole 78 that has the Aluminium A Frame, not suitable for the basic one (XS78) that has to be ground down thin in the middle which weakens it, you can grind it down for the XS78 if required but it will weaken it. But that is how they were made. what they have done for the QB is machine a small groove through the barrel to clear the bolt, so you can use it full size.