A system for removing a tissue specimen through a body opening defining a tissue margin, the system comprising: a shield including a band made of flexible cut-resistant material; the band having an inner surface and an outer surface interconnected by a top end and a bottom end and by a first end and a second end; the band being configured to define a central lumen having a longitudinal axis; the central lumen having a lumen diameter that is perpendicular to the longitudinal axis; wherein the band is split such that the band is movable into a reduced configuration where at least a portion of the outer surface at the first end overlaps and is in juxtaposition with the inner surface at the second end to form a spiral and define an overlapping portion; the shield being configured to have a variable lumen diameter by varying the overlapping portion; and a locking mechanism configured to fix the lumen diameter; the locking mechanism includes a plurality of inner abutments (5020, 5022, 5026) formed on the inner surface and a plurality of outer abutments (5024, 5028, 5030) formed on the outer surface; each of the plurality of inner abutments (5020, 5022, 5026) being configured to contact one of the plurality of outer abutments (5024, 5028, 5030) or the first end to prevent reduction of the lumen diameter in a locked configuration, wherein a portion of the band is jogging outwardly to form a ridge in the inner surface defining an increased lumen diameter; wherein the ridge has an inner ridge surface; characterised in that the inner ridge surface is configured such that the inner surface of the band is substantially flush at an intersection with the overlapping portion of the band. a shield including a band made of flexible cut-resistant material; the band having an inner surface and an outer surface interconnected by a top end and a bottom end and by a first end and a second end; the band being configured to define a central lumen having a longitudinal axis; the central lumen having a lumen diameter that is perpendicular to the longitudinal axis; wherein the band is split such that the band is movable into a reduced configuration where at least a portion of the outer surface at the first end overlaps and is in juxtaposition with the inner surface at the second end to form a spiral and define an overlapping portion; the shield being configured to have a variable lumen diameter by varying the overlapping portion; and a locking mechanism configured to fix the lumen diameter; the locking mechanism includes a plurality of inner abutments (5020, 5022, 5026) formed on the inner surface and a plurality of outer abutments (5024, 5028, 5030) formed on the outer surface; each of the plurality of inner abutments (5020, 5022, 5026) being configured to contact one of the plurality of outer abutments (5024, 5028, 5030) or the first end to prevent reduction of the lumen diameter in a locked configuration, wherein a portion of the band is jogging outwardly to form a ridge in the inner surface defining an increased lumen diameter; wherein the ridge has an inner ridge surface; characterised in that the inner ridge surface is configured such that the inner surface of the band is substantially flush at an intersection with the overlapping portion of the band.