A gyratory crusher frame part comprising: a topshell mountable upon a bottom shell, the topshell having an annular wall extending around a longitudinal axis of the frame part, the annular wall defined between an outward facing surface and an inward facing surface relative to the longitudinal axis; a spider having a plurality of arms formed integrally with the topshell and extending radially outward from a cap positioned at the longitudinal axis, each arm of the plurality of arms having a first portion extending generally in a radially outward direction from the cap and a second portion extending generally in an axial direction from an outer region of the first portion; an annular flange positioned between the second portion of each arm and the annular wall, the flange having an outer circumferential perimeter and an inner circumferential perimeter relative to the longitudinal axis; wherein a radially outermost region of the second portion of each arm is positioned radially inward of the outer circumferential perimeter of the flange; and the second portion of each arm comprises a pair of wings that taper outwardly in the axial direction from the first portion to the flange, each wing of the pair of wings extending substantially in the circumferential direction with the flange; characterised in that: a section of the wall neighbouring the flange comprises a concave section at the outward facing surface and an axially upper first half of the concave section in the axial direction closest to the flange is a substantially uniform curve extending continuously in the circumferential direction around the longitudinal axis and is devoid of axially extending support ribs or shoulders positioned immediately below each of the arms that would otherwise interrupt in the circumferential direction the curve in the upper first half; and a majority of a lower second half of the concave section in the axial direction comprises a curvature profile substantially equal to a curvature profile of the first half in the axial direction. a topshell mountable upon a bottom shell, the topshell having an annular wall extending around a longitudinal axis of the frame part, the annular wall defined between an outward facing surface and an inward facing surface relative to the longitudinal axis; a spider having a plurality of arms formed integrally with the topshell and extending radially outward from a cap positioned at the longitudinal axis, each arm of the plurality of arms having a first portion extending generally in a radially outward direction from the cap and a second portion extending generally in an axial direction from an outer region of the first portion; an annular flange positioned between the second portion of each arm and the annular wall, the flange having an outer circumferential perimeter and an inner circumferential perimeter relative to the longitudinal axis; wherein a radially outermost region of the second portion of each arm is positioned radially inward of the outer circumferential perimeter of the flange; and the second portion of each arm comprises a pair of wings that taper outwardly in the axial direction from the first portion to the flange, each wing of the pair of wings extending substantially in the circumferential direction with the flange; a section of the wall neighbouring the flange comprises a concave section at the outward facing surface and an axially upper first half of the concave section in the axial direction closest to the flange is a substantially uniform curve extending continuously in the circumferential direction around the longitudinal axis and is devoid of axially extending support ribs or shoulders positioned immediately below each of the arms that would otherwise interrupt in the circumferential direction the curve in the upper first half; and a majority of a lower second half of the concave section in the axial direction comprises a curvature profile substantially equal to a curvature profile of the first half in the axial direction.