A bioreactor chamber assembly comprising: a base and a cap configured to be coupled together to define an internal chamber; characterised in that: the base and cap each comprising a plurality of respective interengaging flanges (113, 123) to allow the base and cap to be realisably coupled together axially relative to a longitudinal axis bisecting the base and cap by rotation of at least one of the base and cap around the longitudinal axis; the flanges (113, 123) at each of the base and cap being respectively spaced apart in a direction around the longitudinal axis by gap regions configured to be occupied by at least a portion of the flange (113, 123) of the respective opposing base or cap, each flange (113, 123) having an abutment surface (113S, 123S) extending radially relative to the axis, the abutment surfaces at the base configured to slide over the abutment surfaces at the cap in touching contact by rotation of at least one of the base and cap about the axis such that at least a part of the flange (113S, 123S) of the base and cap overlap in the axial direction to couple and lock the base and cap axially relative to one another; the base and cap each comprising a respective sealing surface (116M, 126M) that may be drawn and mated together axially via an interference fit arrangement by said rotation and the contact between the abutment surfaces (113S, 123S) to provide a fluid tight seal when the base and cap are locked together axially. a base and a cap configured to be coupled together to define an internal chamber; characterised in that: the base and cap each comprising a plurality of respective interengaging flanges (113, 123) to allow the base and cap to be realisably coupled together axially relative to a longitudinal axis bisecting the base and cap by rotation of at least one of the base and cap around the longitudinal axis; the flanges (113, 123) at each of the base and cap being respectively spaced apart in a direction around the longitudinal axis by gap regions configured to be occupied by at least a portion of the flange (113, 123) of the respective opposing base or cap, each flange (113, 123) having an abutment surface (113S, 123S) extending radially relative to the axis, the abutment surfaces at the base configured to slide over the abutment surfaces at the cap in touching contact by rotation of at least one of the base and cap about the axis such that at least a part of the flange (113S, 123S) of the base and cap overlap in the axial direction to couple and lock the base and cap axially relative to one another; the base and cap each comprising a respective sealing surface (116M, 126M) that may be drawn and mated together axially via an interference fit arrangement by said rotation and the contact between the abutment surfaces (113S, 123S) to provide a fluid tight seal when the base and cap are locked together axially. the base and cap each comprising a plurality of respective interengaging flanges (113, 123) to allow the base and cap to be realisably coupled together axially relative to a longitudinal axis bisecting the base and cap by rotation of at least one of the base and cap around the longitudinal axis; the flanges (113, 123) at each of the base and cap being respectively spaced apart in a direction around the longitudinal axis by gap regions configured to be occupied by at least a portion of the flange (113, 123) of the respective opposing base or cap, each flange (113, 123) having an abutment surface (113S, 123S) extending radially relative to the axis, the abutment surfaces at the base configured to slide over the abutment surfaces at the cap in touching contact by rotation of at least one of the base and cap about the axis such that at least a part of the flange (113S, 123S) of the base and cap overlap in the axial direction to couple and lock the base and cap axially relative to one another; the base and cap each comprising a respective sealing surface (116M, 126M) that may be drawn and mated together axially via an interference fit arrangement by said rotation and the contact between the abutment surfaces (113S, 123S) to provide a fluid tight seal when the base and cap are locked together axially.