A medical device comprising: a handle including an actuator member; a shaft extending from the handle and having a deflectable section that is moveable between a linear configuration and an articulated configuration upon application of an axial compression to the shaft upon movement of the actuator member; wherein the shaft comprises at least a first sleeve (122, 120, 930, 950) having a plurality of first keyed slots, wherein each of the first keyed slots comprise a first edge that forms a first keyed portion, a second edge that forms a first key receiving portion, and a third edge and a fourth edge that form a laterally extending portion, wherein the third edge is a vertical lateral edge, the fourth edge is an angled lateral edge that converges to the third edge, and the third edge and the fourth edge are connected by a rounded portion at a radial depth, wherein in the linear configuration the first keyed portion is separated from the first key receiving portion by a gap (938, 958) and upon assuming the articulated configuration the first keyed portion engages the first key receiving portion to nest together and increase a resistance to twisting deformation of the shaft, and wherein the first keyed portion and the first key receiving portion each comprises a first taper angle (960, 942) allowing the first keyed portion to nest together with the first key receiving portion forming a contiguous surface; and wherein the keyed slots comprise a plurality of proximal keyed slots each having a radial depth that varies from an adjacent proximal keyed slot, wherein the radial depth of the proximal keyed slots varies along a straight angle axis angled relative to a longitudinal axis of the shaft, and wherein the third edge and the fourth edge of the proximal keyed slots are tapered relative to each other. a handle including an actuator member; a shaft extending from the handle and having a deflectable section that is moveable between a linear configuration and an articulated configuration upon application of an axial compression to the shaft upon movement of the actuator member; wherein the shaft comprises at least a first sleeve (122, 120, 930, 950) having a plurality of first keyed slots, wherein each of the first keyed slots comprise a first edge that forms a first keyed portion, a second edge that forms a first key receiving portion, and a third edge and a fourth edge that form a laterally extending portion, wherein the third edge is a vertical lateral edge, the fourth edge is an angled lateral edge that converges to the third edge, and the third edge and the fourth edge are connected by a rounded portion at a radial depth, wherein in the linear configuration the first keyed portion is separated from the first key receiving portion by a gap (938, 958) and upon assuming the articulated configuration the first keyed portion engages the first key receiving portion to nest together and increase a resistance to twisting deformation of the shaft, and wherein the first keyed portion and the first key receiving portion each comprises a first taper angle (960, 942) allowing the first keyed portion to nest together with the first key receiving portion forming a contiguous surface; and wherein the keyed slots comprise a plurality of proximal keyed slots each having a radial depth that varies from an adjacent proximal keyed slot, wherein the radial depth of the proximal keyed slots varies along a straight angle axis angled relative to a longitudinal axis of the shaft, and wherein the third edge and the fourth edge of the proximal keyed slots are tapered relative to each other.