The 131B pivot screw is used on all wood Fox and Renard bassoons and contrabassoons, since 1991. It is not used on plastic models. These pivots can be identified visually by the way in which the tapered tip overuns the threads.
131B pivots will not fit keys that were fitted with the older 131 pivots, without modifying the hinge of the key. The pivot sockets at the ends of the key will need to be carefully reamed to fit the new pivots.
The thread size is #6-32. The screws are made of stainless steel.