A protection device for a needle of a needle assembly, the needle assembly including a hub portion for holding the needle , the protection device comprising: an outer casing ; an inner casing engaged with the outer casing , the inner casing having a longitudinal direction and an inner wall defining a cavity configured to receive at least the hub portion ; - a first retainer and a second retainer each defined on said inner wall, attachment means, - aspiration limiting means comprising engaging means for engaging the inner and outer casings, the engaging means retaining a unitary relationship between the outer casing and the inner casing , wherein the inner casing and the outer casing form a unitary part such that upon removal of the protection device from the needle assembly, the unitary part limits deformation of the inner casing along the longitudinal direction, the inner casing including a needle plug for receiving a distal tip of the needle within the inner casing when the hub portion is received in said cavity and to ensure the distal tip of the needle is a distance (Y) from a proximally facing surface of an abutment surface of the outer casing , the needle plug having a proximally facing surface located a distance (X) from the proximally facing surface of the abutment surface , the distance (X) being greater than the distance (Y), and, characterized by : the attachment means comprising at least one bulge defined on the inner wall of the inner casing for removably securing the inner casing to the needle assembly, the at least one bulge configured to define, with the hub portion, at least one sealing line, and as the protection device is removed from the needle assembly, the sealing line is interrupted before the distal tip of the needle separates from the needle plug . an outer casing ; an inner casing engaged with the outer casing , the inner casing having a longitudinal direction and an inner wall defining a cavity configured to receive at least the hub portion ; - a first retainer and a second retainer each defined on said inner wall, - a first retainer and a second retainer each defined on said inner wall, attachment means, - aspiration limiting means comprising engaging means for engaging the inner and outer casings, the engaging means retaining a unitary relationship between the outer casing and the inner casing , - aspiration limiting means comprising engaging means for engaging the inner and outer casings, the engaging means retaining a unitary relationship between the outer casing and the inner casing , wherein the inner casing and the outer casing form a unitary part such that upon removal of the protection device from the needle assembly, the unitary part limits deformation of the inner casing along the longitudinal direction, the attachment means comprising at least one bulge defined on the inner wall of the inner casing for removably securing the inner casing to the needle assembly, the at least one bulge configured to define, with the hub portion, at least one sealing line, and as the protection device is removed from the needle assembly, the sealing line is interrupted before the distal tip of the needle separates from the needle plug . <EOS>