hollow needle 4 appears from the proximal end p and is inserted into an injection site e g a patient 39 s skin the forward movement continues until the syringe holder 22 bottoms out at a first abutment 32 in the housing 2 the travel from the initial position up to this point defines an injection depth i e needle insertion depth when the syringe holder 22 has nearly bottomed out the resilient syringe holder arms 23 have reached a widened portion 2 1 of the housing 2 where they are no longer supported by the inner wall of the housing 2 however since the force required to insert the needle 4 is relatively low the second shoulder 24 will continue to drive forward the syringe holder 22 until proximal travel is halted at the first abutment 32 at this point the syringe holder arms 23 are flexed out by the continued force of the second shoulder 24 and allow it to slip through now the plunger 9 no longer pushes against the syringe holder 22 but against the stopper 6 for expelling the medicament m from the syringe 3 and injecting it into or through the patient 39 s skin when the stopper 6 has nearly bottomed out in the syringe 3 the decoupling member 14 has reached a position where it pushes against the latches 12 in a manner to decouple the retraction sleeve 10 from the housing 2.