The present invention relates to a transfer device for transferring medicament from a medicament container to a syringe with a needle. The transfer device is arranged for transferring accurate dosages of insulin, growth hormone or other medicaments. The accuracy is ensured by the device comprising means for mounting a syringe to the device, the needle piercing a sealing of the device. Opposite the sealing a piston is arranged, said piston being non-releasable engaged with the piston driver during transfer of the medicament. Thereby the piston is not erroneously drawn from the piston driver, which would otherwise lead to incorrect dosing. Furthermore, the device comprises dosing means including the piston driver.