The present invention relates to a needle assembly (1) to be used in combination with a storing device (200) comprising a barrel (8) defining a chamber (9) receiving a product (4) and a piston (2), the assembly (1) comprising: &mdash needle-bearing portion (7) in a first material and movable between an exposed and a retracted positions of the needle (5), &mdash engaging means (8a, 10, 11 and 18,) for securing said needle-bearing portion (7) to said barrel (8) in the exposed position and characterized in that it comprises: &mdash sealing means (15) in a second material for tightly sealing the distal end (9a) of said chamber (9) to said needle-bearing portion (7), &mdash a breakable portion (7a) located between said engaging means (8a, 10, 11 and 18,) and said needle-bearing portion (7), which, when broken and allows independent proximal displacement of said needle-bearing portion (7) relative to said engaging means (8a, 10, 11 and 18,) between said exposed and said retracted positions and said first material being more rigid than said second material. The invention also relates to an injection device (100) comprising said needle assembly (1) and a storing device (200).
