An axis cap module for a hollow winding shaft of a building opening shading device with a curtain for winding and unwinding on the winding shaft, comprising: an inner bushing (5, 9) fastenable on the end side of the winding shaft, and a support socket received in the inner bushing (5, 9) coaxially to the winding shaft, for support of the winding shaft on the end side, which support socket in the direction of the winding shaft axis is held shiftable and preferably with captive fastening between a position extended outwardly and a position retracted inwardly, with the support socket being preferably pretensioned into the position extended outwardly, characterized in that the inner bushing (5, 9) is received in a clamping sleeve insertable into the winding shaft on the end side and at least partially and radially expandable outwardly via the inner bushing (5, 9), and comprises two clamping bushings (5, 9) screwable with each other, which by tightening the screwing in the direction of the winding shaft axis can be moved towards each other and by releasing the screwing can be moved away from each other, the clamping sleeve comprises at least one wedge section concentric with the winding shaft axis and conically tapering on the inner circumference, and at least one clamping bushing, preferably the inner clamping bushing, comprises a counter-wedge section conically tapering on the outer circumference towards the other clamping bushing, in order that the at least one clamping bushing, when tightening the screwing, with its counter-wedge section presses against the wedge section of the clamping sleeve, and thus the axis cap module is stuck in the winding shaft and is released from the winding shaft when the screwing is released. an inner bushing (5, 9) fastenable on the end side of the winding shaft, and a support socket received in the inner bushing (5, 9) coaxially to the winding shaft, for support of the winding shaft on the end side, which support socket in the direction of the winding shaft axis is held shiftable and preferably with captive fastening between a position extended outwardly and a position retracted inwardly, with the support socket being preferably pretensioned into the position extended outwardly, characterized in that the inner bushing (5, 9) is received in a clamping sleeve insertable into the winding shaft on the end side and at least partially and radially expandable outwardly via the inner bushing (5, 9), and comprises two clamping bushings (5, 9) screwable with each other, which by tightening the screwing in the direction of the winding shaft axis can be moved towards each other and by releasing the screwing can be moved away from each other, the clamping sleeve comprises at least one wedge section concentric with the winding shaft axis and conically tapering on the inner circumference, and at least one clamping bushing, preferably the inner clamping bushing, comprises a counter-wedge section conically tapering on the outer circumference towards the other clamping bushing, in order that the at least one clamping bushing, when tightening the screwing, with its counter-wedge section presses against the wedge section of the clamping sleeve, and thus the axis cap module is stuck in the winding shaft and is released from the winding shaft when the screwing is released.