A delivery and detachment system for an implantable intravascular treatment device, the system comprising: an outer delivery tube with a proximal end , an opposite distal end , and a lumen extending axially therethrough; the outer delivery tube having a radially inward stopping member ; a proximal inner tube telescopically receivable in the distal end and axially slidable in a proximal direction within the lumen of the outer delivery tube; the proximal inner tube having a proximal end, an opposite distal end, and a channel extending axially therethrough; the proximal inner tube comprising a proximal section including the proximal end of the proximal inner tube and a distal section including the distal end of the proximal inner tube; wherein the proximal section and the distal section have different outer diameters forming a transition in outer diameter at an interface therebetween; characterized in that the distal section of the proximal inner tube comprises two distal section components connected by an axially separable region ; wherein the two distal section components comprise a first distal section component including the transition and a second distal section component arranged in a distal direction relative to the first distal section component; and a restricting element arranged between an outer surface of the second distal section component and an inner wall of the lumen of the outer delivery tube; when the axially separable region is axially separated: (i) the proximal section of the proximal inner tube is slidable in a proximal direction through the stopping member until the transition in the outer diameter of the first distal section component attached thereto engages the stopping member prohibiting axial movement in the proximal direction; and (ii) the restricting element maintaining in position the second distal section component within the outer delivery tube. an outer delivery tube with a proximal end , an opposite distal end , and a lumen extending axially therethrough; the outer delivery tube having a radially inward stopping member ; a proximal inner tube telescopically receivable in the distal end and axially slidable in a proximal direction within the lumen of the outer delivery tube; the proximal inner tube having a proximal end, an opposite distal end, and a channel extending axially therethrough; the proximal inner tube comprising a proximal section including the proximal end of the proximal inner tube and a distal section including the distal end of the proximal inner tube; wherein the proximal section and the distal section have different outer diameters forming a transition in outer diameter at an interface therebetween; characterized in that the distal section of the proximal inner tube comprises two distal section components connected by an axially separable region ; wherein the two distal section components comprise a first distal section component including the transition and a second distal section component arranged in a distal direction relative to the first distal section component; and a restricting element arranged between an outer surface of the second distal section component and an inner wall of the lumen of the outer delivery tube; when the axially separable region is axially separated: (i) the proximal section of the proximal inner tube is slidable in a proximal direction through the stopping member until the transition in the outer diameter of the first distal section component attached thereto engages the stopping member prohibiting axial movement in the proximal direction; and (ii) the restricting element maintaining in position the second distal section component within the outer delivery tube. <EOS>