A bottle connector for use in a medical fluid transfer arrangement, said bottle connector having an axial direction and a radial direction and comprising: a first generally cylindrical part having a first end and a second end, said first generally cylindrical part comprising a hollow piercing member comprising an inner channel, and a second generally cylindrical part having a first end and a second end, said second generally cylindrical part comprising a bottle coupling member, for coupling said bottle connector to a medical bottle, wherein said first and second generally cylindrical parts (2,3) are pre-connected and are concentrically arranged with respect to each other, said bottle connector having a transport configuration in which said second end of said first generally cylindrical part is located at said first end of said second generally cylindrical part and said piercing member is completely located within said bottle connector, and in which transport configuration the bottle connector has a maximum length (L 1) in the axial direction that is greater than a length (L FP) of the first generally cylindrical part in the axial direction such that the second generally cylindrical part extends in the axial direction past a tip of the piercing member so that the hollow piercing member is completely shielded in the radial direction when the bottle connector is in the transport configuration, and said bottle connector having a fluid transfer configuration in which said second end of said first generally cylindrical part is located at said second end of said second generally cylindrical part so that the bottle connector has a minimum length (L 2) in the axial direction that is less than the maximum length (L 1) in the axial direction, wherein said piercing member is aligned with a central axis through said bottle connector and is placed along said central axis or not more than 3 mm from said central axis as measured in said radial direction of said bottle connector, and said hollow piercing member extends in said axial direction from said first end of said first generally cylindrical part beyond said second end of said first generally cylindrical part, and said tip of the hollow piercing member protrudes slightly past the second end of the first generally cylindrical part in the transport configuration, characterised in that when said bottle connector is in the fluid transfer configuration, said minimum length (L 2) of the bottle connector is identical to the length (L FP) of the first generally cylindrical part. a first generally cylindrical part having a first end and a second end, said first generally cylindrical part comprising a hollow piercing member comprising an inner channel, and a second generally cylindrical part having a first end and a second end, said second generally cylindrical part comprising a bottle coupling member, for coupling said bottle connector to a medical bottle, wherein said first and second generally cylindrical parts (2,3) are pre-connected and are concentrically arranged with respect to each other, said bottle connector having a transport configuration in which said second end of said first generally cylindrical part is located at said first end of said second generally cylindrical part and said piercing member is completely located within said bottle connector, and in which transport configuration the bottle connector has a maximum length (L 1) in the axial direction that is greater than a length (L FP) of the first generally cylindrical part in the axial direction such that the second generally cylindrical part extends in the axial direction past a tip of the piercing member so that the hollow piercing member is completely shielded in the radial direction when the bottle connector is in the transport configuration, and said bottle connector having a fluid transfer configuration in which said second end of said first generally cylindrical part is located at said second end of said second generally cylindrical part so that the bottle connector has a minimum length (L 2) in the axial direction that is less than the maximum length (L 1) in the axial direction, wherein said piercing member is aligned with a central axis through said bottle connector and is placed along said central axis or not more than 3 mm from said central axis as measured in said radial direction of said bottle connector, and said hollow piercing member extends in said axial direction from said first end of said first generally cylindrical part beyond said second end of said first generally cylindrical part, and said tip of the hollow piercing member protrudes slightly past the second end of the first generally cylindrical part in the transport configuration, characterised in that when said bottle connector is in the fluid transfer configuration, said minimum length (L 2) of the bottle connector is identical to the length (L FP) of the first generally cylindrical part.