I bought these to have an extended clamping surface but found that the two sides of the clamp were very poorly formed and finished and that they did not line up resulting in a loss of clamping pressure. When the replacement parts are as bad as the ones I got, I have to spend a lot of time sanding and sanding the surfaces to get them flat and level. something I shouldn't have done. It makes me reconsider the quality of Bessy products.