A conductance valve is configured to be able to adjust the conductance by adjusting the opening degree of an opening formed in part of the wall surface a vacuum vessel. The Fab library of the invention contains at least 109 different Fabs, and in some embodiments, at least 1010 different Fabs. The curved portion of the clamp insert and the curved bore are radially concentric in order to evenly disperse clamping pressures exerted on the clamp insert in all radial directions across the curved portion of the clamp insert to the curved bore. In one embodiment, the first layer is comprised of a biodegradable material that gradually disintegrates when exposed to moisture.