A utensil assembly (150) for use with a surgical instrument (100), comprising the utensil assembly (150): an end effector (154) contiguously disposed to a distal part (124) of an elongated part (120), including the final effector (154) a first jaw member (130) with a tissue contact surface (134), and a second jaw member (140), one of the jaw members being movable relative to the other member of gag, between separate and approximate positions； and a stop member (170) characterized in that said stop member (170) is contiguously disposed to a distal part of the first jaw member (130) and comprising a stop part (174) adapted to engage the tissue and including a body (175), the rotating stop member being with respect to the first jaw member (130), between (i) a first position, in which a significant part of the stop member (170) is externally positioned to the first member (130 ) of jaw and wherein said body (175) defines an angle with respect to said surface (134) of said first jaw member, suitable to facilitate the introduction of tissue between jaw members (130) and (140)； and (ii) a second position in which the tissue can be captured between the first jaw member (130) and the second jaw member (140), where the second jaw member (140) pushes the part (174) of stopping the stop member towards the first jaw member (130), when the at least one jaw member moves towards the approach position, and where a proximal surface (173) of the stop member (170) defines an angle substantially perpendicular with respect to the first jaw member (130) in the second position, suitable to hinder tissue escape.Un conjunto (150) de utensilio para uso con un instrumento quirúrgico (100), comprendiendo el conjunto (150) de utensilio: un efector final (154) dispuesto contiguamente a una parte distal (124) de una parte alargada (120), incluyendo el efector final (154) un primer miembro (130) de mordaza con una superficie (134) de contacto con el tejido, y un segundo miembro (140) de mordaza, si
